sql server 學習記錄

sql-server 基礎： 

一、查看sqlserver的數據表

SELECT name,crdate FROM SysObjects Where XType='U' order by crdate desc

查看數據表的字段

SELECT A.name AS table_name,B.name AS column_name,C.value AS column_description 
FROM sys.tables A INNER JOIN sys.columns B 
ON B.object_id = A.object_id LEFT JOIN sys.extended_properties C 
ON C.major_id = B.object_id AND C.minor_id = B.column_id 
WHERE A.name = '查詢表名'

二、編輯表字段

添加字段： alter table table_name[表名] add field_name[添加字段名] type[字段類型] not null

刪除字段： alter table table_name[表名] drop column field_name[字段名]

修改字段： alter table table_name[表名] alter column field_name[字段名] type[字段類型] not null

 

三、

查詢表的約束：exec sp_helpconstraint [表名]

添加約束：alter table [表名] add constraint [約束名稱] [增長約束類型]

刪除約束關係：alter table [表名] drop constraint [約束名稱]

 

sql-server 優化相關：

一、查詢sql語句執行的耗時和IO消耗
set statistics io on
set statistics time on
-- 要執行的sql語句
set statistics io off
set statistics tine off

二、鏈接查詢優化 

1 select  a.*,b.name  from 
2 S_Linkup a left join u_union b on b.union_id = a.union_id 
3 where  a.CardID = 10 and a.union_id <> (select union_id from S_Card inner join u_union on S_Card.UserID=u_union.UserID where S_Card.CardID = 10)

View Code

能夠優化爲

1 select a.*, b.name from S_Linkup a, u_union b, S_Card c
2 where a.CardID = 10 and a.union_id = b.union_id and a.CardID = c.CardID and b.UserID <> c.UserID

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 3. 行轉列實例 ： PIVOT

go
-- ==========================
-- 銷售季度表，ByYuanbo
-- ==========================
-- drop table SalesByQuarter
create table SalesByQuarter
(
year int,            -- 年份
quarter char(2),    -- 季度
amount money        -- 總額
);

go
-- 0一、插入數據
set nocount on
declare @index int
declare @q int
set @index = 0
declare @year int
while (@index < 30)
begin
    set @year = 2005 + (@index % 4)
    set @q = (CasT((RAND() * 500) as int) % 4) + 1
    insert into SalesByQuarter values(@year, 'Q' + CasT(@q as char(1)), RAND() * 10000.00)
    set @index = @index + 1
end;
go
-- 0二、查詢
select * from SalesByQuarter;
go
-- 0三、傳統 CASE 方法
select year as 年份
,sum(case when quarter = 'Q1' then amount else 0 end) 一季度
,sum(case when quarter = 'Q2' then amount else 0 end) 二季度
,sum(case when quarter = 'Q3' then amount else 0 end) 三季度
,sum(case when quarter = 'Q4' then amount else 0 end) 四季度
from SalesByQuarter
group by year
order by year desc;
go
-- 0四、PIVOT 方法
select year as 年份, Q1 as 一季度, Q2 as 二季度, Q3 as 三季度, Q4 as 四季度 from SalesByQuarter
PIVOT(SUM (amount) FOR quarter IN (Q1, Q2, Q3, Q4) )P
order by year desc;

示例腳本源

View Code