Where 子句

用于指定从一个表或多个表中获取数据的条件。

如果满足给定的条件，即为真（true）时，则从表中返回特定的值。我们可以使用 WHERE 子句来过滤记录，只获取需要的记录。

WHERE 子句不仅可用在 SELECT 语句中，它也可用在 UPDATE、DELETE 语句中，等等。

SELECT column1, column2, columnN 
FROM table_name
WHERE [condition]

-- 数据准备
sqlite> .headers on
sqlite> .mode column
sqlite> select * from COMPANY ;
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0
6           Kim         22          South-Hall  45000.0
7           James       24          Houston     10000.0

实例

-- 获取 AGE 大于等于 25 且工资大于等于 65000.00 的所有记录
sqlite> SELECT * FROM COMPANY WHERE AGE >= 25 AND SALARY >= 65000;
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0

-- 获取AGE 大于等于 25 或工资大于等于 65000.00 的所有记录
sqlite> SELECT * FROM COMPANY WHERE AGE >= 25 OR SALARY >= 65000;
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0

-- 获取AGE 不为 NULL 的所有记录
sqlite> SELECT * FROM COMPANY WHERE AGE IS NOT NULL;
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0
6           Kim         22          South-Hall  45000.0
7           James       24          Houston     10000.0

-- 获取NAME 以 'Ki' 开始的所有记录
sqlite> SELECT * FROM COMPANY WHERE NAME LIKE 'Ki%';
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
6           Kim         22          South-Hall  45000.0

-- 获取 NAME 以 'Ki' 开始的所有记录，'Ki' 之后的字符不做限制
sqlite> SELECT * FROM COMPANY WHERE NAME GLOB 'Ki*';
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
6           Kim         22          South-Hall  45000.0

-- 获取 AGE 的值为 25 或 27 的所有记录
sqlite> SELECT * FROM COMPANY WHERE AGE IN ( 25, 27 );
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
2           Allen       25          Texas       15000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0

-- 获取 AGE 的值既不是 25 也不是 27 的所有记录
sqlite> SELECT * FROM COMPANY WHERE AGE NOT IN ( 25, 27 );
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
3           Teddy       23          Norway      20000.0
6           Kim         22          South-Hall  45000.0
7           James       24          Houston     10000.0

-- 获取 AGE 的值在 25 与 27 之间的所有记录
sqlite> SELECT * FROM COMPANY WHERE AGE BETWEEN 25 AND 27;
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
2           Allen       25          Texas       15000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0