Android下這樣查數據庫會比較酷

時間 2019-11-16

原文原文鏈接

sqlite你們不會陌生。Android原生數據庫就是它了。開發過程當中咱們若是想臨時查看數據庫中的表結構或內容每每要大費周折的將數據庫拷貝出來而後拿工具打開查看，每回都這樣倒騰實在有些麻煩。android

實際上在Android Shell下已經有sqlite3環境了，而且足夠知足基礎的使用。咱們來看一下如何使用。sql

sqlite> .mode column
sqlite> select * from RoutingEntity;
id          current_num  max_num      time           warning_num  type    
----------  ----------  ----------  -------------  ----------  ----------
1           2           2           1518247150757  1           1         
2           2           2           1518247168420  1           1         
複製代碼

此時會獲得一張很漂亮的表結構信息。

也就是說，咱們若是須要獲得這樣的表結構，咱們依次須要輸入

qlite3 xxx.db //打開數據庫
.header on //啓用表頭
.mode column //使用列模式
select * from xxx //查詢某張表

才能夠獲得漂亮的數據。吐槽一句，sqlite的這種設計有點愚蠢，爲何不是一開始就默認啓用表頭和列模式呢？

花式輸出

除了column模式之外，其實還內置了幾組不一樣的模式。分別是:

ascii
csv
column
html
insert
line
list
tabs
tcl

咱們試一下html模式

sqlite> .mode html
sqlite> select * from RoutingEntity;
<TR><TH>id</TH>
<TH>current_num</TH>
<TH>max_num</TH>
<TH>time</TH>
<TH>warning_num</TH>
<TH>type</TH>
</TR>
<TR><TD>1</TD>
<TD>2</TD>
<TD>2</TD>
<TD>1518247150757</TD>
<TD>1</TD>
<TD>1</TD>
</TR>
<TR><TD>2</TD>
<TD>2</TD>
<TD>2</TD>
<TD>1518247168420</TD>
<TD>1</TD>
<TD>1</TD>
</TR>

複製代碼

哇哦，有點炸裂。

再來一組tcl。

sqlite> .mode tcl
sqlite> select * from RoutingEntity;
"id" "current_num" "max_num" "time" "warning_num" "type"
"1" "2" "2" "1518247150757" "1" "1"
"2" "2" "2" "1518247168420" "1" "1 複製代碼

csv

sqlite> .mode csv
sqlite> select * from RoutingEntity;
id,current_num,max_num,time,warning_num,type
1,2,2,1518247150757,1,1
2,2,2,1518247168420,1,1
複製代碼

幫助

若是咱們想知道更多的用法，可使用 .help來打開查看。

sqlite> .help
.backup ?DB? FILE      Backup DB (default "main") to FILE
.bail on|off           Stop after hitting an error.  Default OFF
.binary on|off         Turn binary output on or off.  Default OFF
.clone NEWDB           Clone data into NEWDB from the existing database
.databases             List names and files of attached databases
.dbinfo ?DB?           Show status information about the database
.dump ?TABLE? ...      Dump the database in an SQL text format
                         If TABLE specified, only dump tables matching
                         LIKE pattern TABLE.
.echo on|off           Turn command echo on or off
.eqp on|off            Enable or disable automatic EXPLAIN QUERY PLAN
.exit                  Exit this program
.explain ?on|off?      Turn output mode suitable for EXPLAIN on or off.
                         With no args, it turns EXPLAIN on.
.fullschema            Show schema and the content of sqlite_stat tables
.headers on|off        Turn display of headers on or off
.help                  Show this message
.import FILE TABLE     Import data from FILE into TABLE
.indexes ?TABLE?       Show names of all indexes
                         If TABLE specified, only show indexes for tables
                         matching LIKE pattern TABLE.
.limit ?LIMIT? ?VAL?   Display or change the value of an SQLITE_LIMIT
.log FILE|off          Turn logging on or off.  FILE can be stderr/stdout
.mode MODE ?TABLE?     Set output mode where MODE is one of:
                         ascii    Columns/rows delimited by 0x1F and 0x1E
                         csv      Comma-separated values
                         column   Left-aligned columns.  (See .width)
                         html     HTML <table> code
                         insert   SQL insert statements for TABLE
                         line     One value per line
                         list     Values delimited by .separator strings
                         tabs     Tab-separated values
                         tcl      TCL list elements
.nullvalue STRING      Use STRING in place of NULL values
.once FILENAME         Output for the next SQL command only to FILENAME
.open ?FILENAME?       Close existing database and reopen FILENAME
.output ?FILENAME?     Send output to FILENAME or stdout
.print STRING...       Print literal STRING
.prompt MAIN CONTINUE  Replace the standard prompts
.quit                  Exit this program
.read FILENAME         Execute SQL in FILENAME
.restore ?DB? FILE     Restore content of DB (default "main") from FILE
.save FILE             Write in-memory database into FILE
.scanstats on|off      Turn sqlite3_stmt_scanstatus() metrics on or off
.schema ?TABLE?        Show the CREATE statements
                         If TABLE specified, only show tables matching
                         LIKE pattern TABLE.
.separator COL ?ROW?   Change the column separator and optionally the row
                         separator for both the output mode and .import
.shell CMD ARGS...     Run CMD ARGS... in a system shell
.show                  Show the current values for various settings
.stats on|off          Turn stats on or off
.system CMD ARGS...    Run CMD ARGS... in a system shell
.tables ?TABLE?        List names of tables
                         If TABLE specified, only list tables matching
                         LIKE pattern TABLE.
.timeout MS            Try opening locked tables for MS milliseconds
.timer on|off          Turn SQL timer on or off
.trace FILE|off        Output each SQL statement as it is run
.vfsname ?AUX?         Print the name of the VFS stack
.width NUM1 NUM2 ...   Set column widths for "column" mode
                         Negative values right-justify
複製代碼