语法

SQL 遵循一组称为“语法”的规则和指南。本教程列出了所有的 SQL 基础语法供你快速学习 SQL 之用。

所有的 SQL 语句都以下列关键字之一开始：SELECT、INSERT、UPDATE、DELETE、ALTER、DROP、CREATE、USE、SHOW，并以一个分号（;）结束。

有一点需要特别注意：SQL 不区分大小写，也就是说 SELECT 和 select 在 SQL 语句中有相同的含义。然而，MySQL 在表的名称方面并不遵循此规定。所以，如果你在使用 MySQL 的话，你需要在程序中严格按照它们在数据库中名字进行使用。

本教程列出的所有的例子都在 MySQL 下进行了测试。

SQL SELECT 语句

    SELECT column1, column2....columnN
    FROM   table_name;

SQL DISTINCT 子句

    SELECT DISTINCT column1, column2....columnN
    FROM   table_name;

SQL WHERE 子句

    SELECT column1, column2....columnN
    FROM   table_name
    WHERE  CONDITION;

SQL AND/OR 子句

    SELECT column1, column2....columnN
    FROM   table_name
    WHERE  CONDITION-1 {AND|OR} CONDITION-2;

SQL IN 子句

    SELECT column1, column2....columnN
    FROM   table_name
    WHERE  column_name IN (val-1, val-2,...val-N);

SQL BETWEEN 子句

    SELECT column1, column2....columnN
    FROM   table_name
    WHERE  column_name BETWEEN val-1 AND val-2;

SQL LIKE 子句

    SELECT column1, column2....columnN
    FROM   table_name
    WHERE  column_name LIKE { PATTERN };

SQL ORDER BY 子句

    SELECT column1, column2....columnN
    FROM   table_name
    WHERE  CONDITION
    ORDER BY column_name {ASC|DESC};

SQL GROUP BY 子句

    SELECT SUM(column_name)
    FROM   table_name
    WHERE  CONDITION
    GROUP BY column_name;

SQL COUNT 子句

    SELECT COUNT(column_name)
    FROM   table_name
    WHERE  CONDITION;

SQL HAVING 子句

    SELECT SUM(column_name)
    FROM   table_name
    WHERE  CONDITION
    GROUP BY column_name
    HAVING (arithematic function condition);

SQL CREATE TABLE 语句

    CREATE TABLE table_name(
    column1 datatype,
    column2 datatype,
    column3 datatype,
    .....
    columnN datatype,
    PRIMARY KEY( one or more columns )
    );

SQL DROP TABLE 语句

    DROP TABLE table_name;

SQL CREATE INDEX 语句

    CREATE UNIQUE INDEX index_name
    ON table_name ( column1, column2,...columnN);

SQL DROP INDEX 语句

    ALTER TABLE table_name
    DROP INDEX index_name;

SQL DESC 语句

    DESC table_name;

SQL TRUNCATE TABLE 语句

    TRUNCATE TABLE table_name;

SQL ALTER TABLE 语句（重命名）

    ALTER TABLE table_name RENAME TO new_table_name;

SQL INSERT INTO 语句

    INSERT INTO table_name( column1, column2....columnN)
    VALUES ( value1, value2....valueN);

SQL UPDATE 语句

    UPDATE table_name
    SET column1 = value1, column2 = value2....columnN=valueN
    [ WHERE  CONDITION ];

SQL DELETE 语句