SQLite的 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。您可以使用 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，这些我们将在随后的章节中学习到。
SQLite 的带有 WHERE 子句的 SELECT 语句的基本语法如下：
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<span class="pln">SELECT column1</span><span class="pun">,</span><span class="pln"> column2</span><span class="pun">,</span><span class="pln"> columnN FROM table_name WHERE </span><span class="pun">[</span><span class="pln">condition</span><span class="pun">]</span> |
您还可以使用比较或逻辑运算符指定条件，比如 >、<、=、LIKE、NOT，等等。假设 COMPANY 表有以下记录：
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<span class="pln">ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">1</span> <span class="typ">Paul</span> <span class="lit">32</span> <span class="typ">California</span> <span class="lit">20000.0</span> <span class="lit">2</span> <span class="typ">Allen</span> <span class="lit">25</span> <span class="typ">Texas</span> <span class="lit">15000.0</span> <span class="lit">3</span> <span class="typ">Teddy</span> <span class="lit">23</span> <span class="typ">Norway</span> <span class="lit">20000.0</span> <span class="lit">4</span> <span class="typ">Mark</span> <span class="lit">25</span> <span class="typ">Rich</span><span class="pun">-</span><span class="typ">Mond</span> <span class="lit">65000.0</span> <span class="lit">5</span> <span class="typ">David</span> <span class="lit">27</span> <span class="typ">Texas</span> <span class="lit">85000.0</span> <span class="lit">6</span> <span class="typ">Kim</span> <span class="lit">22</span> <span class="typ">South</span><span class="pun">-</span><span class="typ">Hall</span> <span class="lit">45000.0</span> <span class="lit">7</span> <span class="typ">James</span> <span class="lit">24</span> <span class="typ">Houston</span> <span class="lit">10000.0</span> |
下面的实例演示了 SQLite 逻辑运算符的用法。下面的 SELECT 语句列出了 AGE 大于等于 25 且工资大于等于 65000.00 的所有记录：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT </span><span class="pun">*</span><span class="pln"> FROM COMPANY WHERE AGE </span><span class="pun">>=</span> <span class="lit">25</span><span class="pln"> AND SALARY </span><span class="pun">>=</span> <span class="lit">65000</span><span class="pun">;</span><span class="pln"> ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">4</span> <span class="typ">Mark</span> <span class="lit">25</span> <span class="typ">Rich</span><span class="pun">-</span><span class="typ">Mond</span> <span class="lit">65000.0</span> <span class="lit">5</span> <span class="typ">David</span> <span class="lit">27</span> <span class="typ">Texas</span> <span class="lit">85000.0</span> |
下面的 SELECT 语句列出了 AGE 大于等于 25 或工资大于等于 65000.00 的所有记录：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT </span><span class="pun">*</span><span class="pln"> FROM COMPANY WHERE AGE </span><span class="pun">>=</span> <span class="lit">25</span><span class="pln"> OR SALARY </span><span class="pun">>=</span> <span class="lit">65000</span><span class="pun">;</span><span class="pln"> ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">1</span> <span class="typ">Paul</span> <span class="lit">32</span> <span class="typ">California</span> <span class="lit">20000.0</span> <span class="lit">2</span> <span class="typ">Allen</span> <span class="lit">25</span> <span class="typ">Texas</span> <span class="lit">15000.0</span> <span class="lit">4</span> <span class="typ">Mark</span> <span class="lit">25</span> <span class="typ">Rich</span><span class="pun">-</span><span class="typ">Mond</span> <span class="lit">65000.0</span> <span class="lit">5</span> <span class="typ">David</span> <span class="lit">27</span> <span class="typ">Texas</span> <span class="lit">85000.0</span> |
下面的 SELECT 语句列出了 AGE 不为 NULL 的所有记录，结果显示所有的记录，意味着没有一个记录的 AGE 等于 NULL：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT </span><span class="pun">*</span><span class="pln"> FROM COMPANY WHERE AGE IS NOT NULL</span><span class="pun">;</span><span class="pln"> ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">1</span> <span class="typ">Paul</span> <span class="lit">32</span> <span class="typ">California</span> <span class="lit">20000.0</span> <span class="lit">2</span> <span class="typ">Allen</span> <span class="lit">25</span> <span class="typ">Texas</span> <span class="lit">15000.0</span> <span class="lit">3</span> <span class="typ">Teddy</span> <span class="lit">23</span> <span class="typ">Norway</span> <span class="lit">20000.0</span> <span class="lit">4</span> <span class="typ">Mark</span> <span class="lit">25</span> <span class="typ">Rich</span><span class="pun">-</span><span class="typ">Mond</span> <span class="lit">65000.0</span> <span class="lit">5</span> <span class="typ">David</span> <span class="lit">27</span> <span class="typ">Texas</span> <span class="lit">85000.0</span> <span class="lit">6</span> <span class="typ">Kim</span> <span class="lit">22</span> <span class="typ">South</span><span class="pun">-</span><span class="typ">Hall</span> <span class="lit">45000.0</span> <span class="lit">7</span> <span class="typ">James</span> <span class="lit">24</span> <span class="typ">Houston</span> <span class="lit">10000.0</span> |
下面的 SELECT 语句列出了 NAME 以 'Ki' 开始的所有记录，’Ki' 之后的字符不做限制：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT </span><span class="pun">*</span><span class="pln"> FROM COMPANY WHERE NAME LIKE </span><span class="str">'Ki%'</span><span class="pun">;</span><span class="pln"> ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">6</span> <span class="typ">Kim</span> <span class="lit">22</span> <span class="typ">South</span><span class="pun">-</span><span class="typ">Hall</span> <span class="lit">45000.0</span> |
下面的 SELECT 语句列出了 NAME 以 'Ki' 开始的所有记录，’Ki' 之后的字符不做限制：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT </span><span class="pun">*</span><span class="pln"> FROM COMPANY WHERE NAME GLOB </span><span class="str">'Ki*'</span><span class="pun">;</span><span class="pln"> ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">6</span> <span class="typ">Kim</span> <span class="lit">22</span> <span class="typ">South</span><span class="pun">-</span><span class="typ">Hall</span> <span class="lit">45000.0</span> |
下面的 SELECT 语句列出了 AGE 的值为 25 或 27 的所有记录：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT </span><span class="pun">*</span><span class="pln"> FROM COMPANY WHERE AGE IN </span><span class="pun">(</span> <span class="lit">25</span><span class="pun">,</span> <span class="lit">27</span> <span class="pun">);</span><span class="pln"> ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">2</span> <span class="typ">Allen</span> <span class="lit">25</span> <span class="typ">Texas</span> <span class="lit">15000.0</span> <span class="lit">4</span> <span class="typ">Mark</span> <span class="lit">25</span> <span class="typ">Rich</span><span class="pun">-</span><span class="typ">Mond</span> <span class="lit">65000.0</span> <span class="lit">5</span> <span class="typ">David</span> <span class="lit">27</span> <span class="typ">Texas</span> <span class="lit">85000.0</span> |
下面的 SELECT 语句列出了 AGE 的值既不是 25 也不是 27 的所有记录：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT </span><span class="pun">*</span><span class="pln"> FROM COMPANY WHERE AGE NOT IN </span><span class="pun">(</span> <span class="lit">25</span><span class="pun">,</span> <span class="lit">27</span> <span class="pun">);</span><span class="pln"> ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">1</span> <span class="typ">Paul</span> <span class="lit">32</span> <span class="typ">California</span> <span class="lit">20000.0</span> <span class="lit">3</span> <span class="typ">Teddy</span> <span class="lit">23</span> <span class="typ">Norway</span> <span class="lit">20000.0</span> <span class="lit">6</span> <span class="typ">Kim</span> <span class="lit">22</span> <span class="typ">South</span><span class="pun">-</span><span class="typ">Hall</span> <span class="lit">45000.0</span> <span class="lit">7</span> <span class="typ">James</span> <span class="lit">24</span> <span class="typ">Houston</span> <span class="lit">10000.0</span> |
下面的 SELECT 语句列出了 AGE 的值在 25 与 27 之间的所有记录：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT </span><span class="pun">*</span><span class="pln"> FROM COMPANY WHERE AGE BETWEEN </span><span class="lit">25</span><span class="pln"> AND </span><span class="lit">27</span><span class="pun">;</span><span class="pln"> ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">2</span> <span class="typ">Allen</span> <span class="lit">25</span> <span class="typ">Texas</span> <span class="lit">15000.0</span> <span class="lit">4</span> <span class="typ">Mark</span> <span class="lit">25</span> <span class="typ">Rich</span><span class="pun">-</span><span class="typ">Mond</span> <span class="lit">65000.0</span> <span class="lit">5</span> <span class="typ">David</span> <span class="lit">27</span> <span class="typ">Texas</span> <span class="lit">85000.0</span> |
下面的 SELECT 语句使用 SQL 子查询，子查询查找 SALARY > 65000 的带有 AGE 字段的所有记录，后边的 WHERE 子句与 EXISTS 运算符一起使用，列出了外查询中的 AGE 存在于子查询返回的结果中的所有记录：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT AGE FROM COMPANY WHERE EXISTS </span><span class="pun">(</span><span class="pln">SELECT AGE FROM COMPANY WHERE SALARY </span><span class="pun">></span> <span class="lit">65000</span><span class="pun">);</span><span class="pln"> AGE </span><span class="pun">----------</span> <span class="lit">32</span> <span class="lit">25</span> <span class="lit">23</span> <span class="lit">25</span> <span class="lit">27</span> <span class="lit">22</span> <span class="lit">24</span> |
下面的 SELECT 语句使用 SQL 子查询，子查询查找 SALARY > 65000 的带有 AGE 字段的所有记录，后边的 WHERE 子句与 > 运算符一起使用，列出了外查询中的 AGE 大于子查询返回的结果中的年龄的所有记录：
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<span class="pln">sqlite</span><span class="pun">></span><span class="pln"> SELECT </span><span class="pun">*</span><span class="pln"> FROM COMPANY WHERE AGE </span><span class="pun">></span> <span class="pun">(</span><span class="pln">SELECT AGE FROM COMPANY WHERE SALARY </span><span class="pun">></span> <span class="lit">65000</span><span class="pun">);</span><span class="pln"> ID NAME AGE ADDRESS SALARY </span><span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="pun">----------</span> <span class="lit">1</span> <span class="typ">Paul</span> <span class="lit">32</span> <span class="typ">California</span> <span class="lit">20000.0 from:<a href="http://www.runoob.com/sqlite/sqlite-where-clause.html">http://www.runoob.com/sqlite/sqlite-where-clause.html</a></span> |