語法

SQL 語法

SQL 遵循一組稱為“語法”的規(guī)則和指南。本教程列出了所有的 SQL 基礎(chǔ)語法供你快速學(xué)習(xí) SQL 之用。

所有的 SQL 語句都以下列關(guān)鍵字之一開始：SELECT、INSERT、UPDATE、DELETE、ALTER、DROP、CREATE、USE、SHOW，并以一個分號（;）結(jié)束。

有一點需要特別注意：SQL 不區(qū)分大小寫，也就是說 SELECT 和 select 在 SQL 語句中有相同的含義。然而，MySQL 在表的名稱方面并不遵循此規(guī)定。所以，如果你在使用 MySQL 的話，你需要在程序中嚴(yán)格按照它們在數(shù)據(jù)庫中名字進(jìn)行使用。

本教程列出的所有的例子都在 MySQL 下進(jìn)行了測試。

SQL SELECT 語句

    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 語句

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

SQL DROP TABLE 語句

    DROP TABLE table_name;

SQL CREATE INDEX 語句

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

SQL DROP INDEX 語句

    ALTER TABLE table_name
    DROP INDEX index_name;

SQL DESC 語句

    DESC table_name;

SQL TRUNCATE TABLE 語句

    TRUNCATE TABLE table_name;

SQL ALTER TABLE 語句（重命名）

    ALTER TABLE table_name RENAME TO new_table_name;

SQL INSERT INTO 語句

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

SQL UPDATE 語句

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

SQL DELETE 語句

    DELETE FROM table_name
    WHERE  {CONDITION};

SQL CREATE DATABASE 語句

    CREATE DATABASE database_name;

SQL DROP DATABASE 語句

    DROP DATABASE database_name;

SQL USE 語句

    USE database_name;

SQL COMMIT 語句

    COMMIT;

SQL ROLLBACK 語句

    ROLLBACK;