[Sqlite]移动嵌入式数据库Sqlite的日常SQL操作语句汇总

序言: 嵌入式数据库Sqlite的基本sql使用汇总,使用测试起来,与关系型数据库mysql在语法上有很多的相似之处,先准备测试数据: CREATE TABLE COMPANY(ID INT NOT NULL, NAME VARCHAR(20),AGE INT,ADDRESS VARCHAR(20),SALARY DECIMAL(7,2)); INSERT INTO CO

序言:

嵌入式数据库Sqlite的基本sql使用汇总,使用测试起来,与关系型数据库mysql在语法上有很多的相似之处,先准备测试数据:

CREATE TABLE COMPANY(ID INT NOT NULL, NAME VARCHAR(20),AGE INT,ADDRESS VARCHAR(20),SALARY DECIMAL(7,2));

INSERT INTO "COMPANY" VALUES(1,'Paul',32,'California',20000);

INSERT INTO "COMPANY" VALUES(2,'Allen',25,'Texas',15000);

INSERT INTO "COMPANY" VALUES(3,'Teddy',23,'Norway',20000);

INSERT INTO "COMPANY" VALUES(4,'Mark',25,'Rich-Mond',65000);

INSERT INTO "COMPANY" VALUES(5,'David',27,'Texas',85000);

INSERT INTO "COMPANY" VALUES(6,'Kim',22,'South-Hall',45000);

INSERT INTO "COMPANY" VALUES(7,'James',24,NULL,10000);

INSERT INTO "COMPANY" VALUES(8,'Xiaoteng',29,NULL,NULL);

1,分组统计排序

GROUP BY 进行分组统计数据,命令如下:

sqlite> SELECT NAME, SUM(SALARY) SALARY_SUM, COUNT(1) COUNT_NUM FROM COMPANY GROUP BY NAME;

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ORDER BY 进行排序,命令如下:

sqlite> SELECT NAME, SUM(SALARY) SALARY_SUM, COUNT(1) COUNT_NUM FROM COMPANY GROUP BY NAME ORDER BY SALARY_SUM ASC;

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HAVING 字句过滤数据记录,命令如下:

SELECT c.*,COUNT(1) COUNT_NUM FROM COMPANY c GROUP BY c.NAME HAVING (COUNT_NUM) > 1 ORDER BY COUNT_NUM ;

PS:在一个查询中,HAVING 子句必须放在 GROUP BY 子句之后,必须放在 ORDER BY 子句之前。下面是包含 HAVING 子句的 SELECT 语句的语法:

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2,Limit分页统计语句

SQLite 的 LIMIT 子句用于限制由 SELECT 语句返回的数据数量。

第一页取值SQL: SELECT * FROM COMPANY ORDER BY ID LIMIT 0,3; 也可以从一个特定的偏移开始提取记录,从第四位开始提取 3 个记录,使用OFFSET关键字,SELECT * FROM COMPANY ORDER BY ID LIMIT 3 OFFSET 0;PS:首页从0开始取值。
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第二页取值SQL: SELECT * FROM COMPANY ORDER BY ID LIMIT 3,3; 也可以从一个特定的偏移开始提取记录,从第四位开始提取 3 个记录,使用OFFSET关键字,SELECT * FROM COMPANY ORDER BY ID LIMIT 3 OFFSET 3;如下图所示:
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3,Glob匹配字句

SQLite 的 GLOB 运算符是用来匹配通配符指定模式的文本值。如果搜索表达式与模式表达式匹配,GLOB 运算符将返回真(true),也就是 1。与 LIKE 运算符不同的是,GLOB 是大小写敏感的,对于下面的通配符,它遵循 UNIX 的语法。

星号 (*)

问号 (?)

星号(*)代表零个、一个或多个数字或字符。问号(?)代表一个单一的数字或字符。这些符号可以被组合使用。

下面一些实例演示了 带有 '*' 和 '?' 运算符的 GLOB 子句不同的地方:

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下面是一个实例,它显示 COMPANY 表中 AGE 以 2 开头的所有记录,如下所示:

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下面是一个实例,它显示 COMPANY 表中 ADDRESS 文本里包含一个连字符(-)的所有记录:

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4,Distinct关键字过滤重复记录

SQLite 的 DISTINCT 关键字与 SELECT 语句一起使用,来消除所有重复的记录,并只获取唯一一次记录。

有可能出现一种情况,在一个表中有多个重复的记录。当提取这样的记录时,DISTINCT 关键字就显得特别有意义,它只获取唯一一次记录,而不是获取重复记录。

5,字符串连接操作

问题地址:http://bbs.csdn.net/topics/390886865

sqlite> CREATE TABLE t1(id int, name varchar(60));

sqlite> INSERT INTO "t1" VALUES(4,'1@test.cn');

sqlite> select * from t1;

id name

---------- ----------

4 1@test.cn

sqlite> update t1 set name=(id/2)||substr(name,instr(name,'@'),length(name)-instr(name,'@')+1) where id=4;

sqlite> select * from t1;

id name

---------- ----------

4 2@test.cn

sqlite>

6,对Null值的处理

往表里面录入Null值

sqlite> INSERT INTO COMPANY(ID,NAME,AGE,ADDRESS,SALARY) VALUES(8,'Xiaoteng',29,NULL,18000);

sqlite>

修改某个字段为null值

sqlite> UPDATE COMPANY SET SALARY = NULL WHERE ID=8;

sqlite>

查询为null的记录

sqlite> SELECT * FROM COMPANY WHERE ADDRESS IS NULL;

ID NAME AGE ADDRESS SALARY

---------- ---------- ---------- ---------- ----------

7 James 24 10000

8 Xiaoteng 29

sqlite>

查询不为null的记录

sqlite> SELECT * FROM COMPANY WHERE ADDRESS IS NOT NULL;

ID NAME AGE ADDRESS SALARY

---------- ---------- ---------- ---------- ----------

1 Paul 32 California 20000

2 Allen 25 Texas 15000

3 Teddy 23 Norway 20000

4 Mark 25 Rich-Mond 65000

5 David 27 Texas 85000

6 Kim 22 South-Hall 45000

sqlite>

7,子查询

SELECt中的基本语法如下:

SELECT column_name [, column_name ]

FROM table1 [, table2 ]

WHERE column_name OPERATOR

(SELECT column_name [, column_name ]

FROM table1 [, table2 ]

[WHERE])

实例如下:

sqlite> SELECT * FROM COMPANY WHERE ID IN (SELECT ID FROM COMPANY WHERE SALARY > 45000);

INSERT语句中的子查询使用,基本语法:

INSERT INTO table_name [ (column1 [, column2 ]) ]

SELECT [ *|column1 [, column2 ]

FROM table1 [, table2 ]

[ WHERE VALUE OPERATOR ]

实例如下:

sqlite> INSERT INTO COMPANY_BKP

SELECT * FROM COMPANY

WHERE ID IN (SELECT ID

FROM COMPANY) ;

UPDATE语句中的子查询使用,基本语法如下:

UPDATE table

SET column_name = new_value

[ WHERE OPERATOR [ VALUE ]

(SELECT COLUMN_NAME

FROM TABLE_NAME)

[ WHERE) ]

实例如下:

sqlite> UPDATE COMPANY

SET SALARY = SALARY * 0.50

WHERE AGE IN (SELECT AGE FROM COMPANY_BKP

WHERE AGE >= 27 );

DELETE语句中的子查询使用,语法如下:

DELETE FROM TABLE_NAME

[ WHERE OPERATOR [ VALUE ]

(SELECT COLUMN_NAME

FROM TABLE_NAME)

[ WHERE) ]

实例如下:

sqlite> DELETE FROM COMPANY

WHERE AGE IN (SELECT AGE FROM COMPANY_BKP

WHERE AGE > 27 );

8,EXPLAIN分析

没有建立索引之前,分析都是表扫描:

sqlite> EXPLAIN SELECT * FROM COMPANY WHERE Salary < 20000;

addr opcode p1 p2 p3 p4 p5 comment

---------- ---------- ---------- ---------- ---------- ---------- ---------- ----------

0 Trace 0 0 0 00

1 Integer 20000 1 0 00

2 Goto 0 16 0 00

3 OpenRead 0 2 0 5 00

4 Rewind 0 14 0 00

5 Column 0 4 2 00

6 Ge 1 13 2 collseq(BI 6b

7 Column 0 0 4 00

8 Column 0 1 5 00

9 Column 0 2 6 00

10 Column 0 3 7 00

11 Column 0 4 8 00

12 ResultRow 4 5 0 00

13 Next 0 5 0 01

14 Close 0 0 0 00

15 Halt 0 0 0 00

16 Transactio 0 0 0 00

17 VerifyCook 0 1 0 00

18 TableLock 0 2 0 COMPANY 00

19 Goto 0 3 0 00

sqlite> EXPLAIN QUERY PLAN SELECT * FROM COMPANY WHERE Salary < 20000;

order from detail

---------- ---------- -------------

0 0 TABLE COMPANY

sqlite>

建立索引,再进行EXPLAIN分析查看结果,走了idx_sal索引扫描:

sqlite> CREATE INDEX idx_sal ON COMPANY(SALARY);

sqlite> EXPLAIN SELECT * FROM COMPANY WHERE Salary < 20000;

addr opcode p1 p2 p3 p4 p5 comment

---------- ---------- ---------- ---------- ---------- ---------- ---------- ----------

0 Trace 0 0 0 00

1 Integer 20000 1 0 00

2 Goto 0 25 0 00

3 OpenRead 0 2 0 5 00

4 OpenRead 1 3 0 keyinfo(1, 00

5 Affinity 2 0 0 cb 00

6 Rewind 1 22 2 0 00

7 SCopy 1 2 0 00

8 IsNull 2 22 0 00

9 Affinity 2 1 0 cb 00

10 IdxGE 1 22 2 1 00

11 Column 1 0 3 00

12 IsNull 3 21 0 00

13 IdxRowid 1 3 0 00

14 Seek 0 3 0 00

15 Column 0 0 4 00

16 Column 0 1 5 00

17 Column 0 2 6 00

18 Column 0 3 7 00

19 Column 1 0 8 00

20 ResultRow 4 5 0 00

21 Next 1 10 0 00

22 Close 0 0 0 00

23 Close 1 0 0 00

24 Halt 0 0 0 00

25 Transactio 0 0 0 00

26 VerifyCook 0 2 0 00

27 TableLock 0 2 0 COMPANY 00

28 Goto 0 3 0 00

sqlite> EXPLAIN QUERY PLAN SELECT * FROM COMPANY WHERE Salary < 20000;

order from detail

---------- ---------- --------------------------------

0 0 TABLE COMPANY WITH INDEX idx_sal

sqlite>

9,删除重复数据并且保留最新一条记录

录入测试数据

sqlite> .dump

PRAGMA foreign_keys=OFF;

BEGIN TRANSACTION;

CREATE TABLE COMPANY(ID INT NOT NULL, NAME VARCHAR(20),AGE INT,ADDRESS VARCHAR(20),SALARY DECIMAL(7,2));

INSERT INTO "COMPANY" VALUES(2,'Allen',25,'Texas',15000);

INSERT INTO "COMPANY" VALUES(3,'Teddy',23,'Norway',20000);

INSERT INTO "COMPANY" VALUES(4,'Mark',25,'Rich-Mond',65000);

INSERT INTO "COMPANY" VALUES(5,'David',27,'Texas',85000);

INSERT INTO "COMPANY" VALUES(6,'Kim',22,'South-Hall',45000);

INSERT INTO "COMPANY" VALUES(7,'James',24,'Houston',10000);

INSERT INTO "COMPANY" VALUES(7,'James',28,'Houston',20000);

INSERT INTO "COMPANY" VALUES(4,'Mark',29,'Rich-Mond',95000);

COMMIT;

sqlite>

查看重复记录数

sqlite> select * from company order by name;

ID NAME AGE ADDRESS SALARY

---------- ---------- ---------- ---------- ----------

2 Allen 25 Texas 15000

5 David 27 Texas 85000

7 James 24 Houston 10000

7 James 28 Houston 20000

6 Kim 22 South-Hall 45000

4 Mark 25 Rich-Mond 65000

4 Mark 29 Rich-Mond 95000

3 Teddy 23 Norway 20000

sqlite>

通过rowid来删除重复记录

sqlite> DELETE FROM COMPANY WHERE rowid NOT IN(SELECT MAX(rowid) rowid FROM COMPANY GROUP BY NAME);

sqlite>

再查看最新的数据记录,已经删除了重复NAME的记录

sqlite> select * from company;

ID NAME AGE ADDRESS SALARY

---------- ---------- ---------- ---------- ----------

2 Allen 25 Texas 15000

3 Teddy 23 Norway 20000

5 David 27 Texas 85000

6 Kim 22 South-Hall 45000

7 James 28 Houston 20000

4 Mark 29 Rich-Mond 95000

sqlite>

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参考文章:http://www.w3cschool.cc/sqlite/sqlite-tutorial.html