SQL common keywords examples and tricks

時間 2019-11-08

標籤 sql common keywords examples tricks 欄目 SQL 简体版

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Case Sensitive Check

1. Return names contain upper case

Select id, name from A where name<>lower(name) collate SQL_Latin1_General_CP1_CS_AS

2. Return same name but diff case

Select id, A.name, B.name from A inner join B on A.name=B.name where A.name<>B.name collate SQL_Latin1_General_CP1_CS_AS

Case when

http://www.javashuo.com/article/p-tcpctorc-bc.htmlmysql

1. Calculate sum of different group

國家（country）    人口（population）
中國    600
美國    100
加拿大    100
英國    200
法國    300
日本    250
德國    200
墨西哥    50
印度    250sql

Result:express

洲    人口
亞洲    1100
北美洲    250
其餘    700session

SELECT  SUM(population),
        CASE country
                WHEN '中國'     THEN '亞洲'
                WHEN '印度'     THEN '亞洲'
                WHEN '日本'     THEN '亞洲'
                WHEN '美國'     THEN '北美洲'
                WHEN '加拿大'  THEN '北美洲'
                WHEN '墨西哥'  THEN '北美洲'
        ELSE '其餘' END
FROM    Table_A
GROUP BY CASE country
                WHEN '中國'     THEN '亞洲'
                WHEN '印度'     THEN '亞洲'
                WHEN '日本'     THEN '亞洲'
                WHEN '美國'     THEN '北美洲'
                WHEN '加拿大'  THEN '北美洲'
                WHEN '墨西哥'  THEN '北美洲'
        ELSE '其餘' END;

2. Calculate total amount of different pay level

SELECT
        CASE WHEN salary <= 500 THEN '1'
             WHEN salary > 500 AND salary <= 600  THEN '2'
             WHEN salary > 600 AND salary <= 800  THEN '3'
             WHEN salary > 800 AND salary <= 1000 THEN '4'
        ELSE NULL END salary_class,
        COUNT(*)
FROM    Table_A
GROUP BY
        CASE WHEN salary <= 500 THEN '1'
             WHEN salary > 500 AND salary <= 600  THEN '2'
             WHEN salary > 600 AND salary <= 800  THEN '3'
             WHEN salary > 800 AND salary <= 1000 THEN '4'
        ELSE NULL END;

3. Calculate sum of different group with multiple columns

國家（country）    性別（sex）    人口（population）
中國    1    340
中國    2    260
美國    1    45
美國    2    55
加拿大    1    51
加拿大    2    49
英國    1    40
英國    2    60app

Result:
國家    男    女
中國    340    260
美國    45    55
加拿大    51    49
英國    40    60dom

SELECT country,
       SUM( CASE WHEN sex = '1' THEN 
                      population ELSE 0 END),  --male population
       SUM( CASE WHEN sex = '2' THEN 
                      population ELSE 0 END)   --female population
FROM  Table_A
GROUP BY country;

Cast & Convert (change data type)

Cast is compatible to both sql server and mysql, convert is designed for sql server, and it can have more styles and specially useful for datetime (check datetime part)ide

select cast(1.23 as int) --return 1
select convert( int,1.23) --return 1

Create a column of numbers (usually ids)

DECLARE @startnum INT=1000 --start
DECLARE @endnum INT=1020 --end 
;
WITH gen AS (
    SELECT @startnum AS num
    UNION ALL
    --change number+ i to adjust gap i
    SELECT num+3 FROM gen WHERE num+1<=@endnum 
)
SELECT * FROM gen
option (maxrecursion 10000)

num
1000
1003
1006
1009
1012
1015
1018
1021oop

Create a column of strings from one long string

;WITH Split(stpos,endpos)
        AS(
            SELECT 0 AS stpos, CHARINDEX(',','Alice,Jack,Tom') AS endpos 
            UNION ALL
            SELECT endpos+1, CHARINDEX(',','Alice,Jack,Tom',endpos+1) FROM Split WHERE endpos > 0
        )  
        --LTRIM RTRIM to get rid of white space before start or after end of str
        SELECT RTRIM(LTRIM(SUBSTRING('Alice,Jack,Tom',stpos,COALESCE(NULLIF(endpos,0),LEN('Alice,Jack,Tom')+1)-stpos))) as name into #temp
        FROM Split

name
Alice
Jack
Tomsqlserver

Create a table of lots of strings in same column

SELECT * into #temp FROM (VALUES (1,'Alice'),(2,'Jack'),(3,'Tom')) AS t(id,name)

id name
1 Alice
2 Jack
3 Tomui

Create a temp table (copy a table)

1. From a existing table, no need create table (not copy indexing or primary key)

Select id, name, 'placeholder' as sex into #temp from A

Trick to copy a table structure(cols and datatype) but not content

--0=1 to not copy any rows
Select id, name into #temp from A where 0=1 

--the above query equals to 
select id, name into #temp from #temp1
delete from #temp1

2. Create temp table (lifespan: current session, drop on close tab)

create table #tmpStudent(Id int ,Name varchar(50),Age int) insert into #tmpStudent select id,name,age from #tmpStudentIDENTITY(1,1) PRIMARY KEY

3. Global temp table (##temp, can visit from other tab, drop on close tab where it is created)

4. Using table variable (lifespan: current transaction, drop after running query block)

DECLARE @temp Table ( Id int, Name varchar(20), Age int )

Datetime

1. Current date/datetime/UTC date, convert datetime to date only

select GETDATE()
select GETUTCDATE()
select cast(GETDATE() as date)  --date only
SELECT convert(date, GETDATE() ) --date only

2. Tomorrow/yesterday, next/last hour (simple nearby datetime)

-- add or minus is on day basis
select GETDATE()+1 --tomorrow
select GETDATE()-1 --yesterday

-- need to be 24.0 to return float
select GETDATE()+1.0/24 --next hour
select GETDATE()-1.0/24/2 --Last 30 min

3. Add/minus any period for a date (use with 4.datediff)

--result is already datetime
select DATEADD(yy,-2,'07/23/2009 13:23:44') --2 years ago
select DATEADD(mm,5, DATEADD(dd,10,GETDATE())) --5 month and 10 days later

The datepart can be 'year' or 'yy' or 'yyyy', all same

4. Datediff of 2 datetime ( =2nd-1st, result is + or - interger)

select DATEDIFF(mi,GETDATE()+1.0/24,  GETDATE()-1.0/24)  -- return -120
select DATEDIFF(dd,'2019-11-23', '2019-12-23')  --return 30

5. Generate any datetime

select cast('2019-10-23 23:30:59:883' as datetime) --'yyyy-mm-dd' 
select cast('2019/10/23 23:30:59:883' as datetime) --'yyyy/mm/dd' use ':' for ms
select cast('10-23-2019 23:30:59.883' as datetime) --'mm-dd-yyyy' use '.' for ms
select cast('10/23/2019 23:30:59.883' as datetime) --'mm/dd/yyyy'
--same to use convert
SELECT convert(date, '07/23/2009' )

6. Get day/week/month/year part of a datetime

--these pairs are same to get dd,mm,yy part of a datetime, return integer
select Datepart(dd,GETDATE()),day(GETDATE())
select Datepart(mm,GETDATE()),month(GETDATE())
select Datepart(yyyy,GETDATE()),year(GETDATE())

select Datepart(dy,'2019-08-11') --get day of year: 223

select datename(mm,'2000-5-17')  --return 'May'
select datename(weekday,'2000-5-17') --return 'Wednesday'

7. Convert datetime format (input need to be datetime only, result is a string)

-- not working!!!! return '2019-05-17', as it detect input is string, 103 is ignored
select convert(varchar, '2019-05-17', 103)

--input is datetime, reutrn formatted string '17/05/2019'
select convert(varchar, cast('2019-05-17' as datetime), 103)

for a full list of datetime format code (smilar to 103)

Format #	Query	Sample
DATE ONLY FORMATS
1	select convert(varchar, getdate(), 1)	12/30/06
2	select convert(varchar, getdate(), 2)	06.12.30
3	select convert(varchar, getdate(), 3)	30/12/06
4	select convert(varchar, getdate(), 4)	30.12.06
5	select convert(varchar, getdate(), 5)	30-12-06
6	select convert(varchar, getdate(), 6)	30 Dec 06
7	select convert(varchar, getdate(), 7)	Dec 30, 06
10	select convert(varchar, getdate(), 10)	12-30-06
11	select convert(varchar, getdate(), 11)	06/12/30
12	select convert(varchar, getdate(), 12)	061230
23	select convert(varchar, getdate(), 23)	2006-12-30
101	select convert(varchar, getdate(), 101)	12/30/2006
102	select convert(varchar, getdate(), 102)	2006.12.30
103	select convert(varchar, getdate(), 103)	30/12/2006
104	select convert(varchar, getdate(), 104)	30.12.2006
105	select convert(varchar, getdate(), 105)	30-12-2006
106	select convert(varchar, getdate(), 106)	30 Dec 2006
107	select convert(varchar, getdate(), 107)	Dec 30, 2006
110	select convert(varchar, getdate(), 110)	12-30-2006
111	select convert(varchar, getdate(), 111)	2006/12/30
112	select convert(varchar, getdate(), 112)	20061230

TIME ONLY FORMATS
8	select convert(varchar, getdate(), 8)	00:38:54
14	select convert(varchar, getdate(), 14)	00:38:54:840
24	select convert(varchar, getdate(), 24)	00:38:54
108	select convert(varchar, getdate(), 108)	00:38:54
114	select convert(varchar, getdate(), 114)	00:38:54:840

DATE & TIME FORMATS
0	select convert(varchar, getdate(), 0)	Dec 12 2006 12:38AM
9	select convert(varchar, getdate(), 9)	Dec 30 2006 12:38:54:840AM
13	select convert(varchar, getdate(), 13)	30 Dec 2006 00:38:54:840AM
20	select convert(varchar, getdate(), 20)	2006-12-30 00:38:54
21	select convert(varchar, getdate(), 21)	2006-12-30 00:38:54.840
22	select convert(varchar, getdate(), 22)	12/30/06 12:38:54 AM
25	select convert(varchar, getdate(), 25)	2006-12-30 00:38:54.840
100	select convert(varchar, getdate(), 100)	Dec 30 2006 12:38AM
109	select convert(varchar, getdate(), 109)	Dec 30 2006 12:38:54:840AM
113	select convert(varchar, getdate(), 113)	30 Dec 2006 00:38:54:840
120	select convert(varchar, getdate(), 120)	2006-12-30 00:38:54
121	select convert(varchar, getdate(), 121)	2006-12-30 00:38:54.840
126	select convert(varchar, getdate(), 126)	2006-12-30T00:38:54.840
127	select convert(varchar, getdate(), 127)	2006-12-30T00:38:54.840

Delete duplicate rows (entire same or partialy same)

0. create example table

create table #Student (id int, Class int, Score int )
insert into #Student values(1,1,88)
insert into #Student values(2,1,66)
insert into #Student values(3,2,30)
insert into #Student values(4,2,70)
insert into #Student values(5,2,60)
insert into #Student values(6,3,70)
insert into #Student values(7,3,80)

1. Select duplicate rows based on 1 column

select * from students where id in (
    select id FROM students
    group by id having count(*)>1
)

2. Select duplicate rows based on multiple columns

select * from students a
right join (
    select firstname, lastname from students
    group by firstname, lastname having count(*)>1
) b
on a.firstname=b.firstname and a.lastname=b.lastname

3. Select rows that has unique combination of colums(filter out all duplicate rows)

select * from students except(
    select a.* --need to select all columns here
from students a
    right join (
        select firstname, lastname from students 
        group by firstname, lastname having count(*)>1
    ) b
    on a.firstname=b.firstnameand a.lastname =b.lastname 
)

4. Select/delete rows of totally identical values

select distinct * from tableName --save the result equals to delete duplicated rows already

5. Delete duplicate rows in table which has unique id

delete from #temp
where id not in(
    select   max(id)   from   #temp
    group   by   col1, col2 --the columns used when checking duplicate
    having count(*)>1
)

6. Delete duplicate rows in table which does not have id

6.1 Delete directly from original table by "Partition" keyword

WITH tempVw AS (
    SELECT 
        *,
        ROW_NUMBER() OVER ( --over() is required for Row_Number()
            PARTITION BY --this reset the rowNumber to 1 for different group
                col1, col2 --which used as identifier to check duplicate
            ORDER BY  --order by is required in Over()
                col1, col2 --keep same as above
        ) row_num
     FROM 
        YourTable
)
delete FROM tempVw WHERE row_num > 1
select * from YourTable --duplicated rows should be removed in original table

6.2 Add unique ID first so it is similar as point 5

--Use views to add rowId for table without unique id
with tempVw as(
    select ROW_NUMBER() over (order by SurveyTypeid, surveyid ) as rowid,*
    from YourTable
)
--define 2 views together, tempVw2 is all duplicated rows
,tempVw2 as (
    select rowid,a.col1,a.col2
    from tempVw a
    right join (
        select col1, col2 from tempVw
        group by col1, col2 having count(*)>1
    ) b
    on a.col1=b.col1 and a.col2=b.col2
) 

--query after view, delete rows in view will delete original table
delete  from tempVw where rowid in (
    --return all duplicated rows except 1 row for each group that we will keep
    select rowid from tempVw2 where rowid not in (
        --return 1 row for each identifier of duplicated rows
        select min (rowid) from tempVw2 group by col1, col2 having count(*)>1
    )
)
select * from YourTable --duplicated rows should be removed in original table

Dynamic SQL (EXEC)

1. Query without quote

declare @sql varchar(max)= 'select * from #StudentMarks'
exec (@sql)

2. If there is any single quote inside query, double it

--the end has 3 quote because: double single quote + end quote of the query varchar
declare @sql varchar(max)= 'select *  from #StudentMarks where name=''Alice''' 
exec (@sql)

3. if you have single quote inside a string, you need doule it

-- output: 2019's, you need double the quote as it is in a string: 2019''s
select *,'2019''s' as category from #StudentMarks where name='Alice'

declare @sql varchar(max)= 'select *,''2019''''s'' as category from #StudentMarks where name=''Alice'''
exec (@sql)

4. If you add a number var to a dynamic query, you need to cast to varchar, no need for extra quote

declare @Math int=90
declare @sql varchar(max)= 'select *  from #StudentMarks where Math='+cast(@Math as varchar)+' and Science=40'
exec (@sql)

5. If you add a string var to a dynamic query, you need quote the input, and double the quote

declare @Name varchar(max)='Alice'
--first 3 quotes = double the left quote of @Name + end quote of 1st part of query
-- 4 quotes = start quote of 3rd part+ double the right quote of @Name + end quote of 3rd part
declare @sql varchar(max)= 'select *  from #StudentMarks where name='''+@Name+''''
exec (@sql)

6. Connect multiple query string together

--double the left and right quote around Alice inside the query
declare @sql2 varchar(max)=' where name = ''Alice'' '
--do not forget to leave a space after each query
declare @sql varchar(max)= 'select *  from #StudentMarks '+ @sql2
exec (@sql)

Except (check difference between 2 tables of same colums) & Intersect

1. Rows which included in A but not B

Select * from A except Select * from B

2. Return any diff bewteen A and B

Select * from A except Select * from B union all Select * from B except Select * from A

3. Return duplicated rows between A and B

Select * from A Intersect Select * from B

EXEC output to Variable

1. Using table variable

declare @temp table(id int,Name varchar(50),sex varchar(10))
declare @sql varchar(max)= 'select id,name,''male'' from student where id<3'
insert into @temp exec (@sql)

2. Using sp_executesql

DECLARE @sql nvarchar(1000), @input varchar(75)='Fenton', @output varchar(75)
SET @sql = 'SELECT top 1 @firstname=firstname FROM [AspNetUsers] WHERE surname = @surname'
EXECUTE sp_executesql @sql, N'@surname varchar(75),@firstname varchar(75) OUTPUT', @surname = @input, @firstname=@output OUTPUT
select @output

Exists

1. To add any condition for the select (Same as if)

Select col1, col2 from A where exists (Select 1 from B where id=99) --inside exists you can select 1 or anything, it will return TRUE equally

2. To select new user in A but not in B

Select id, name from A where not exists (Select 1 from B where B.id=A.id) 

--this equals to use IN keyword
Select id, name from A where id not in (Select id from B)

Group by (only work with count(), AVG(), MAX(), MIN(), Sum() )

--student number for each class
select class,count (*) as total from Student group by class 
--average score for each class
select class,avg(score) as AvgScore from Student group by class 
--highest score for each class
select class,max(score) as HighestScore from Student group by class 
--total donation for each class
select class,sum(donation) as TotalDonation from Student group by class

To get top x rows or the xth place in each group, use row_number()

Import data from excel

SELECT * --INTO #Cars
FROM OPENROWSET('Microsoft.ACE.OLEDB.12.0',
'Excel 12.0 Xml;HDR=YES;Database=C:\cars.xlsx','SELECT * FROM [sheet1$]');

Insert into

1. Mutiple rows with values

insert into #temp(id,name) values (1,'Alice'),(2, 'Jack')

2. From existing tables

insert into #temp(id,name, sex) select id, name,'male' from students where sex=1

3. From exec (Assign EXEC output to Variable)

declare @temp table(id int,Name varchar(50),sex varchar(10))
declare @sql varchar(max)= 'select id,name,''male'' from student where id<3'
insert into @temp exec (@sql)

Join

1. cross join

(https://blog.csdn.net/xiaolinyouni/article/details/6943337)

Select * from A cross join B
Select * from A,B --same as above

2. Left join, right join, inner join

Left join: contains all rows from left table A, if A.key=B.key, return result in new table, if multiple B.key match A.key, return multiple rows, if no B.key match, return row with null values

inner join: only return if A.key=B.key, can be one to one or one to many

Like and Regex

(http://www.sqlservertutorial.net/sql-server-basics/sql-server-like/)

The percent wildcard (%): any string of zero or more characters.
The underscore (_) wildcard: any single character.
The [list of characters] wildcard: any single character within the specified set.
The [character-character]: any single character within the specified range.
The [^]: any single character not within a list or a range.

Not start with special symbol, 3rd character is number or letter

Select * from where name LIKE ' [^.$#@-]_ [a-z0-9]%'

Login history delete for SSMS

C:\Users\*********\AppData\Roaming\Microsoft\SQL Server Management Studio\18.0\UserSettings.xml

Open it in any Texteditor like Notepad++
ctrl+f for the username to be removed
then delete the entire <Element>.......</Element> block that surrounds it.

Pivot, unpivot (merge multiple cols or split into multiple cols)

1. Convert multiple columns into one

0. Create example table

Name Math Science English
Alice 90 40 60
Tom 30 20 10

CREATE TABLE #StudentMarks(Name varchar(100),Math int,Science int, English int)
insert into #StudentMarks values('Alice',90,40,60)
insert into #StudentMarks values('Tom',30,20,10)

1.1 Result

name subject marks
Alice Math 90
Alice Science 40
Alice English 60
Tom Math 30
Tom Science 20
Tom English 10

1.2 Convert multiple columns into one (unpivot)

--can be any col in #studentmarks + subject+ marks
select  name, subject, marks 
from #studentmarks  
unpivot
(
  marks --marks: actual values
  for subject in (Math, Science, English) --subject: col names
) a

1.3 Convert multiple columns into one (cross join)

select name, subject, 
    case subject --this select the right subject score value to put in new col
    when 'Maths' then math
    when 'Science' then science
    when 'English' then english
    end as Marks
from #studentmarks
Cross Join (values('Maths'),('Science'),('English')) AS Subjct(Subject)

2. Split one column value to different columns

if it is static and only a few diff values, use "case when" (search 'case when' in blog)

0. Create sample example

CREATE TABLE #Source(
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Name] [varchar](50) NULL,
    [FieldCode] [varchar](50) NULL,
    [Value] int NULL
) ON [PRIMARY]


INSERT INTO #Source([Name],[FieldCode],[Value]) 
    SELECT 'Alice','English',60  UNION ALL
    SELECT 'Jack','Math',70  UNION ALL
    SELECT 'Tom','Science',80  UNION ALL
    SELECT 'Tom','Math',75  UNION ALL
    SELECT 'Tom','English',57  UNION ALL
    SELECT 'Jack','English',80  UNION ALL
    SELECT 'Alice','Science',100

2.1 Pivot to dynamic split one col to multiple

--**rename the reference col as name, sourceCol as 'fieldcode', value as 'value'
DECLARE    @SourceTable VARCHAR(500)='#Source'
DECLARE    @place_holder_len VARCHAR(500)='1000'

--*****if get error 'String or binary data would be truncated', need increase size of this str
--1000 length, this is random string placeholder of the col data length when using PIVOT function 
DECLARE @place_holder VARCHAR(8000)= space(@place_holder_len); --this should work as above

--The max len of varchar is 8000, so need to divide sql str into a few varchar
DECLARE @sql_current_str VARCHAR(8000) =''
DECLARE @sql_str1 VARCHAR(8000) =''
DECLARE @sql_str2 VARCHAR(8000) =''
DECLARE @sql_str3 VARCHAR(8000) =''
DECLARE @sql_str4 VARCHAR(8000) =''
DECLARE @sql_str5 VARCHAR(8000) =''
DECLARE @sql_str6 VARCHAR(8000) =''
DECLARE @sql_str7 VARCHAR(8000) =''
DECLARE @sql_str8 VARCHAR(8000) =''
DECLARE @sql_str9 VARCHAR(8000) =''
DECLARE @sql_str10 VARCHAR(8000) =''
DECLARE @sql_str998 VARCHAR(8000) ='' --to replace the placeholder to empty string and select result
DECLARE @sql_str999 VARCHAR(8000) ='' --to replace the placeholder to empty string and select result
DECLARE @all_survey_data_cols VARCHAR(8000)

DECLARE @col VARCHAR(8000)='' --current col in loop of all the cols           
DECLARE @count int =1              
DECLARE @index int =1

DECLARE @FieldTable Table (fieldcode varchar(1000))
SET @sql_str1 = 'select distinct (fieldcode) from '+ @SourceTable +' (nolock)'
Insert @FieldTable Exec (@sql_str1)
 
select *,ROW_NUMBER() over (order by fieldcode)  as i into #Field_ASC from (select * from @FieldTable) a

select @count=max(i) from #Field_ASC
select @all_survey_data_cols = ISNULL(@all_survey_data_cols + ',','') + QUOTENAME(fieldcode) FROM (select fieldcode from #Field_ASC) a

SET @sql_str1 = '

    SELECT distinct name,data.*  into #temp
    FROM '+ @SourceTable +'
    inner join (
        SELECT * FROM 
        (select fieldcode,'''+@place_holder+''' as zz from #Field_ASC) p  PIVOT 
        (max(zz) FOR fieldcode IN ( '+ @all_survey_data_cols +') ) AS pvt 
    ) data  on 1=1
'

while (@index<@count+1)
begin
    select @col = fieldcode  from #Field_ASC where i=@index

    --this is to divide the sql string as max size of varchar is 8000
    if (len(@sql_str9)>7000)
    begin 
        set @sql_current_str= @sql_str10
    end
    else if (len(@sql_str8 )>7000)
    begin 
        set @sql_current_str= @sql_str9
    end
    else if (len(@sql_str7 )>7000)
    begin 
        set @sql_current_str= @sql_str8
    end
    else if (len(@sql_str6 )>7000)
    begin 
        set @sql_current_str= @sql_str7
    end
    else if (len(@sql_str5 )>7000)
    begin 
        set @sql_current_str= @sql_str6
    end
    else if (len(@sql_str4 )>7000)
    begin 
        set @sql_current_str= @sql_str5
    end
    else if (len(@sql_str3 )>7000)
    begin 
        set @sql_current_str= @sql_str4
    end
    else if (len(@sql_str2 )>7000)
    begin 
        set @sql_current_str= @sql_str3
    end
    else if (len(@sql_str1 )>7000)
    begin 
        set @sql_current_str= @sql_str2
    end
    else
    begin
        set @sql_current_str= @sql_str1
    end

    set @sql_current_str =@sql_current_str +'
        update  a
        set a.['+@col+']=  CONVERT(varchar(8000), b.value)
        from #temp a
        inner join (select *   from '+ @SourceTable +' (nolock)    
        ) b
        on a.name=b.name and b.fieldcode='''+@col+ ''''
 
    
    --this is to divide the sql string as max size of varchar is 8000
    if (len(@sql_str9)>7000)
    begin 
        set @sql_str10 = @sql_current_str
    end
    else if (len(@sql_str8 )>7000)
    begin 
        set @sql_str9 = @sql_current_str
    end
    else if (len(@sql_str7 )>7000)
    begin 
        set @sql_str8 = @sql_current_str
    end
    else if (len(@sql_str6 )>7000)
    begin 
        set @sql_str7 = @sql_current_str
    end
    else if (len(@sql_str5 )>7000)
    begin 
        set @sql_str6 = @sql_current_str
    end
    else if (len(@sql_str4 )>7000)
    begin 
        set @sql_str5 = @sql_current_str
    end
    else if (len(@sql_str3 )>7000)
    begin 
        set @sql_str4 = @sql_current_str
    end
    else if (len(@sql_str2 )>7000)
    begin 
        set @sql_str3 = @sql_current_str
    end
    else if (len(@sql_str1 )>7000)
    begin 
        set @sql_str2 = @sql_current_str
    end
    else
    begin
        set @sql_str1 = @sql_current_str
    end

    set @index=@index+1

end

set @index=1
while (@index<@count+1)
begin
    select @col = fieldcode from #Field_ASC where i=@index
    if (len(@sql_str998)>7000) --if exceed 8000 size then store the rest in new str
    begin
        set @sql_str999 =@sql_str999 +' update #temp set ['+ @col  +'] ='''' where  len(['+ @col+'])  =0'  --replace placeholder by ''
    end
    else
    begin
        set @sql_str998 =@sql_str998 +' update #temp set ['+ @col  +'] ='''' where  len(['+ @col+'])   =0'--replace placeholder by ''
    end
    set @index=@index+1
end

set @sql_str999 =@sql_str999 + '  select * from #temp'

PRINT ( @sql_str1 + @sql_str2+ @sql_str3 + @sql_str4 + @sql_str5 + @sql_str6 + @sql_str7+ @sql_str8 + @sql_str9 + @sql_str10 + @sql_str998+ @sql_str999 ) 
EXEC ( @sql_str1 + @sql_str2+ @sql_str3 + @sql_str4 + @sql_str5 + @sql_str6 + @sql_str7+ @sql_str8 + @sql_str9 + @sql_str10 + @sql_str998+ @sql_str999 ) 

--to check if the sql string is overflow
print ('string 1: ' + cast (len ( @sql_str1 ) as varchar(100)) + ' string 2: ' +  cast (len ( @sql_str2) as varchar(100)) 
+' string 3: ' +  cast (len ( @sql_str3 ) as varchar(100))+' string 4: ' +  cast (len ( @sql_str5 ) as varchar(100))
+' string 5: ' +   cast (len ( @sql_str5 ) as varchar(100)) +' string 6: ' + cast (len ( @sql_str6 ) as varchar(100)) 
+ ' string 7: ' +  cast (len ( @sql_str7) as varchar(100)) +' string 8: ' +  cast (len ( @sql_str8 ) as varchar(100))
+' string 9: ' +  cast (len ( @sql_str9 ) as varchar(100))+' string 10: ' +   cast (len ( @sql_str10 ) as varchar(100)) 
+' string 998: ' +   cast (len ( @sql_str998 ) as varchar(100))+' string 999: ' + cast (len ( @sql_str999 ) as varchar(100)))


drop table #Field_ASC

View Code

Random id (GUID), string, number

1. Random Guid

select NEWID() --315FC5A3-BE07-41BB-BE4F-75055729FA5B

2. Random string

SELECT CONVERT(varchar(255), NEWID())

3. Random number (round to integer)

SELECT RAND() -- 0<=decimal<1 
SELECT RAND()*15+5; -- 5<=decimal<20 (if include 20 need *16)

SELECT FLOOR(22.6) --22
SELECT CEILING(22.6) --23
SELECT ROUND(22.6,0) -- 23.0
SELECT ROUND(22.6,-1) --20.0

Row_number(), Rank() and Dense_rank() (must use with over(order by ...) )

1. Add row id by row_number()

select *,row_number() over(order by class) rowid from #Student

2. if there is identiacal value for the colomn used for order by: Rank() and Dense_rank()

select *,rank() over(order by class) rowid from #Student --if 1st has 2 pp, next is 3rd
select *,dense_rank() over(order by class) rowid from #Student --if 1st has 2 pp, next is 2nd

3. Partition by: Assign row id for different group, each group start with 1

select *,row_number() over(partition by class order by class) rowid from #Student

4. Select top 2, the 2nd second place for each group

select * from (
    select *,row_number() over(partition by class order by class) rowid from #Student  
)a where rowid<2

select * from (
    select *,row_number() over(partition by class order by class) rowid from #Student  
)a where rowid=2

Search any "keyword" in database

1. Search keyword for all cols in one table

USE [YourDB]
GO

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO


/*

    [SearchOneTable]  'ASPnetusers','2019'
    [SearchOneTable]  'ASPnetusers','8',1,1,0

*/


CREATE PROC [dbo].[SearchOneTable]
(
    @TableName nvarchar(256),
    @Keyword nvarchar(100),
    @SearchDate bit=0,
    @SearchNumber bit=0,
    @SearchString bit=1
    
)
AS
BEGIN
    SET NOCOUNT ON

    if PARSENAME(@TableName, 2) is null
    begin
        set @TableName = 'dbo.' + QUOTENAME(@TableName, '"')
    end
    
    SET @Keyword  = QUOTENAME('%' + @Keyword + '%','''')
    DECLARE @ColumnName nvarchar(128) = ''
    DECLARE @ColumnNameTableVar table(ColumnName nvarchar(128)) --table var to store exec result into var
    DECLARE @sql varchar(max)=''
    DECLARE @StringTypes varchar(1000)='''char'', ''varchar'', ''nchar'', ''nvarchar'''
    DECLARE @DateTypes varchar(1000)='''date'', ''time'', ''datetime'', ''timestamp'''
    DECLARE @NumberTypes varchar(1000)='''int'', ''decimal'', ''float'', ''bit'''
    DECLARE @results TABLE(ColumnName nvarchar(370), ColumnValue nvarchar(3630))

    IF @TableName <> ''
    BEGIN
        WHILE (@TableName IS NOT NULL) AND (@ColumnName IS NOT NULL)
        BEGIN

            set @sql='SELECT MIN(QUOTENAME(COLUMN_NAME))
                FROM  INFORMATION_SCHEMA.COLUMNS
                WHERE  TABLE_SCHEMA    = PARSENAME('''+@TableName+''', 2)
                    AND  TABLE_NAME    = PARSENAME('''+@TableName+''', 1)
                    AND  QUOTENAME(COLUMN_NAME) > '''+@ColumnName+'''
                    AND  DATA_TYPE IN (' + 
                        case when @SearchDate=1 and @SearchNumber=0 then @DateTypes +' , '
                            when @SearchDate=0 and @SearchNumber=1 then @NumberTypes +' , '
                            when @SearchDate=1 and @SearchNumber=1 then @DateTypes +' , ' + @NumberTypes +' , '
                            else ' ' end
                    + case when @SearchString=1 then @StringTypes else '''''' end
                    + ')'

            delete from @ColumnNameTableVar --empty table first
            insert into @ColumnNameTableVar exec (  @sql )
            select top 1 @ColumnName=ColumnName from @ColumnNameTableVar        

            IF @ColumnName IS NOT NULL
            BEGIN  
                INSERT INTO @results
                EXEC
                (
                    'SELECT ''' + @TableName + '.' + @ColumnName + ''', LEFT(' + @ColumnName + ', 3630) 
                    FROM ' + @TableName + ' WITH (NOLOCK) ' +
                    ' WHERE ' + @ColumnName + ' LIKE ' + @Keyword
                )
            END
        END    
    END
        
    SELECT ColumnName, ColumnValue FROM @results

END
GO

View Code

2. Search keyword for all cols in all tables (Extremely slow!!!)

USE [YourDB]
GO

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO



/*
*******don't use it in large db, which will be extremely slow**********

    [SearchAllTables] 'survey' 

*/
CREATE PROC [dbo].[SearchAllTables]
(
    @Keyword nvarchar(100),
    @SearchDate bit=0,
    @SearchNumber bit=0,
    @SearchString bit=1
)
AS
BEGIN
    
    SET NOCOUNT ON
    SET @Keyword = QUOTENAME('%' + @Keyword + '%','''')

    CREATE TABLE #Results (ColumnName nvarchar(370), ColumnValue nvarchar(3630))

    DECLARE @TableName nvarchar(256)=''
    DECLARE @ColumnName nvarchar(128) 
    DECLARE @ColumnNameTableVar table(ColumnName nvarchar(128)) --table var to store exec result into var
    DECLARE @sql varchar(max)=''
    DECLARE @StringTypes varchar(1000)='''char'', ''varchar'', ''nchar'', ''nvarchar''  '
    DECLARE @DateTypes varchar(1000)='''date'', ''time'', ''datetime'', ''timestamp'''
    DECLARE @NumberTypes varchar(1000)='''int'', ''decimal'', ''float'', ''bit'''

    WHILE @TableName IS NOT NULL
    BEGIN
        SET @ColumnName = ''
        SET @TableName = 
        (
            SELECT MIN(QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME))
            FROM     INFORMATION_SCHEMA.TABLES
            WHERE         TABLE_TYPE = 'BASE TABLE'
                AND    QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME) > @TableName
                AND    OBJECTPROPERTY(
                        OBJECT_ID(
                            QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME)
                             ), 'IsMSShipped'
                               ) = 0
        )

        WHILE (@TableName IS NOT NULL) AND (@ColumnName IS NOT NULL)
        BEGIN

            set @sql='SELECT MIN(QUOTENAME(COLUMN_NAME))
                FROM  INFORMATION_SCHEMA.COLUMNS
                WHERE  TABLE_SCHEMA    = PARSENAME('''+@TableName+''', 2)
                    AND  TABLE_NAME    = PARSENAME('''+@TableName+''', 1)
                    AND  QUOTENAME(COLUMN_NAME) > '''+@ColumnName+'''
                    AND  DATA_TYPE IN (' + 
                        case when @SearchDate=1 and @SearchNumber=0 then @DateTypes +' , '
                            when @SearchDate=0 and @SearchNumber=1 then @NumberTypes +' , '
                            when @SearchDate=1 and @SearchNumber=1 then @DateTypes +' , ' + @NumberTypes +' , '
                            else ' ' end
                    + case when @SearchString=1 then @StringTypes else '''''' end
                    + ')'

            delete from @ColumnNameTableVar --empty table first
            insert into @ColumnNameTableVar exec (  @sql )
            select top 1 @ColumnName=ColumnName from @ColumnNameTableVar    

            IF @ColumnName IS NOT NULL
            BEGIN
                INSERT INTO #Results
                EXEC
                (
                    'SELECT ''' + @TableName + '.' + @ColumnName + ''', LEFT(' + @ColumnName + ', 3630) 
                    FROM ' + @TableName + 'WITH (NOLOCK) ' +
                    ' WHERE ' + @ColumnName + ' LIKE ' + @Keyword
                )
            END
        END    
    END

    SELECT ColumnName, ColumnValue FROM #Results
END
GO

View Code

3. Search keyword for all the cols name in all tables

--to search "keyword" in any cols, in any tables of db
SELECT
b.name as tables, a.name as cols
FROM
sys.columns as a inner join sys.tables as b on a.object_id=b.object_id
where a.name like '%keyword%'
order by b.name

4. Search keyword in whole text of the proc (may not working very well if proc is very long)

--to search "keyword" in stored procedure whole text
SELECT ROUTINE_NAME, ROUTINE_DEFINITION
FROM INFORMATION_SCHEMA.ROUTINES
WHERE ROUTINE_DEFINITION LIKE '%keyword%'
AND ROUTINE_TYPE='PROCEDURE'

Short Keys for text selection

(https://www.mssqltips.com/sqlservertip/2786/column-and-block-text-selection-using-sql-server-management-studio/)

1. Using SHIFT+ALT+(arrow key or cursor) to Select block of values among multiple rows

2. Using CTRL+SHIFT+END to Select Text till end (CTRL+ END can move cursor to end)

3. Using CTRL+SHIFT+HOME to Select Text till start (CTRL+HOME can move cursor to end)

4. User CTRL+ arrow key can move cursor jump between words not letters

String edit

Note: SQL index start from 1 not 0

1. left and right

select left('hello world',5) --return: hello
select right('hello world!',6) --return:world!

2. Substring

select substring('hello world',7,5) --return: world

3. Replace (by expression or by index)

select REPLACE('123456','34','new') --return 12new56
select stuff('123456',3,2,'new') --same as above, start index=3, length=2

4. Split (not exist in sql, need use LEFT+ RIGHT + CHARINDEX)

--split 'hello world' by space
select left('hello world',CHARINDEX(' ','hello world')-1) 
select right('hello world',len('hello world')-CHARINDEX(' ','hello world'))

5. Delete white space

SELECT LTRIM('   Sample   '); --return 'Sample '
SELECT RTRIM('   Sample   '); --return ' Sample'

6. Delete enter, tab, space

--char(13)+CHAR(10) = enter
print 'first line'+char(13)+CHAR(10)+'Second line' --2 lines
--char(9) is tab, the outsode replace delete all space
print REPLACE(REPLACE(REPLACE(REPLACE('first line
Second line',CHAR(13),''),CHAR(10),''),CHAR(9),''),' ','')

7. Search a regex in string

SELECT PATINDEX('%[mo]%', 'W3Schools.com'); --return m or o which appear first

8. Repeat string a few times

select REPLICATE('hello world ',3) --return: hello world hello world hello world

9. Revers a string by characters

select REVERSE('1234567') --return 7654321

10. Create an empty fixed length string (only contains spaces)

select 'a'+SPACE(5)+'b' --return a     b

Top

1. select rows between m and n place of highest score

select top 2 * from ( --between 4 and 5, 5-4+1=2
    select top 5 * from #Student order by score desc)a
order by score

2. Select 2nd second place by add row_number()

-- if there are multiple highest score, will select highest score
select * from (
    select *,row_number() over( order by score desc) rowid from #Student  
)a where rowid=2
--if there are multiple highest score, still select second highest score 
select * from (
    select *,rank() over( order by score desc) rowid from #Student  
)a where rowid=2
-- rowid between m and n -- rows between order of the m place to n place

Transaction

1. Begin, rollback,commit tran

Declare @isDebug bit=0
begin tran

-- insert/update/delete queries    

if @isDebug=0 and @@error=0 --prod run and no errors
begin
    commit tran
end
else -- test run or any error
begin
    rollback tran
end

2. trasaction with try/catch

Declare @isDebug bit=1
BEGIN TRY
    BEGIN tran    
        if @isDebug=0 --test run
        begin 
            -- insert/update/delete queries    
        end
        else --prod run
        begin
            -- insert/update/delete queries
        end

    COMMIT tran --commit if above code has no error
END TRY
BEGIN CATCH
    ROLLBACK tran --if any error jump to this to rollback
    select ERROR_NUMBER() as ErrorNumber, ERROR_MESSAGE() as ErrorMessage, ERROR_PROCEDURE() as ErrorProcedure
END CATCH

Output (to log result along with query)

1. You can output deleted or inserted rows with the query

CREATE TABLE #temp (ID INT, Val VARCHAR(100))  
INSERT #temp (ID, Val)  VALUES (1,'FirstVal')  
INSERT #temp (ID, Val)  VALUES (2,'SecondVal')  

CREATE TABLE #log (ID INT, Val VARCHAR(100), Query VARCHAR(100))  
 
SELECT * FROM #temp 

INSERT #temp (ID, Val) output inserted.ID,inserted.Val,'Insert' into #log 
VALUES (3,'ThirdVal')  

--you can also output both deleted and inserted values
Update #temp set Val='NewVal' 
output Deleted.ID, Deleted.Val,'Delete' into #log
where id=3

Update #temp set Val='NewVal' 
output inserted.ID,inserted.Val,'Insert' into #log
where id=3

DELETE FROM #temp  
OUTPUT Deleted.ID, Deleted.Val,'Delete'  into #log 
WHERE ID IN (1,2)  
 
SELECT * FROM #log  
SELECT * FROM #temp 

DROP TABLE #temp  
DROP TABLE #log

Union, Union All

1. Union not return duplicated rows (by duplicated mean all the values are exactly same)

2. Union All return all rows include duplicated rows

3. Both Union and Union all need to have exactly same number of total columns (col name can be diff but type need to be same)

4. Union All is much faster than Union

Update one colomn from column in another table

UPDATE  a
SET     a.marks = b.marks
FROM    tempDataView a
        INNER JOIN tempData b
            ON a.Name = b.Name

Variables (declare, set, select)

1. Declare multiple vars and initialize the value

declare @a int =1, @b varchar(max)='abc'

2. Set can only set single values

set @a=2

3. Set values by using query

set @a=(select 2)

4. Select can assign value to multiple vars

select @a=2, @b='new'

5. Select to assign values by query

select top 1 @a=ClientId, @b=Surname from [AspNetUsers]

6. EXEC to a variable

DECLARE @sql nvarchar(1000), @input varchar(75)='Fenton', @output varchar(75)
SET @sql = 'SELECT top 1 @firstname=firstname FROM [AspNetUsers] WHERE surname = @surname'
EXECUTE sp_executesql @sql, N'@surname varchar(75),@firstname varchar(75) OUTPUT', @surname = @input, @firstname=@output OUTPUT
select @output

View (with ... as )

**delete or update view will influence original table, delete or update or insert values will influence on view

with StudentVw as(
    select top 100 ROW_NUMBER() over (order by SurveyTypeid, surveyid ) as rowid,*
    from ##temp order by channelid -- if use order by must have top keyword
)
select * from StudentVw --must come with a query and only 1 query

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