**SQL 分类：** **SQL 语句主要可以划分为以下 4 个类别。** **DDL（Data Definition Languages）语句：**数据定义语言，这些语句定义了不同的数据段、数据库、表、列、索引等数据库对象的定义。常用的语句关键字主要包括 create、drop、alter等。 ```sql CREATE <![TEMPORARY|TEMP]> TABLE [IF NOT EXISTS] tbl_name ( column type [ NULL | NOT NULL ] [ UNIQUE ] [ DEFAULT value ] [column_constraint_clause | PRIMARY KEY } [ ... ] ] [, PRIMARY KEY ( column [, ...] ) ] [, CHECK ( condition ) ] [, table constraint ] ) DROP [TEMPORARY] TABLE [IF EXISTS] tbl_name [, tbl_name] ... [RESTRICT | CASCADE] ALTER TABLE table [ * ] ADD [<!COLUMN>] column type ALTER TABLE table [ * ] DROP [ COLUMN ] column ALTER TABLE table [ * ] MODIFY [<!COLUMN>] column { <!SET> DEFAULT value | DROP DEFAULT } ALTER TABLE table [ * ] MODIFY [<!COLUMN>] column column_constraint ALTER TABLE table [ * ] RENAME [<!COLUMN>] column TO newcolumn ALTER TABLE table RENAME TO newtable ALTER TABLE table ADD table_constraint ALTER INDEX index_name {VISIBLE | INVISIBLE} ``` **DQL（Data Query Language SELECT ）数据查询语言，select语句。** ```sql SELECT [ALL | DISTINCT | DISTINCTROW ] [HIGH_PRIORITY] [STRAIGHT_JOIN] [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT] [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS] select_expr [, select_expr ...] [FROM table_references [PARTITION partition_list] [WHERE where_condition] [GROUP BY {col_name | expr | position} [ASC | DESC], ... [WITH ROLLUP]] [HAVING where_condition] [WINDOW window_name AS (window_spec) [, window_name AS (window_spec)] ...] [ORDER BY {col_name | expr | position} [ASC | DESC], ...] [LIMIT {[offset,] row_count | row_count OFFSET offset}] [INTO OUTFILE 'file_name' [CHARACTER SET charset_name] export_options | INTO DUMPFILE 'file_name' | INTO var_name [, var_name]] [FOR UPDATE | LOCK IN SHARE MODE]] [FOR {UPDATE | SHARE} [OF tbl_name [, tbl_name] ...] [NOWAIT | SKIP LOCKED] | LOCK IN SHARE MODE]] ``` **DML（Data Manipulation Language）语句：**数据操纵语句，用于添加、删除、更新和查询数据库记录，并检查数据完整性，常用的语句关键字主要包括 insert、delete、udpate 。(增添改） ```sql INSERT INTO tbl_name [ ( column [, ...] ) ] { VALUES ( expression [, ...] ) | SELECT query } //demo INSERT INTO tbl_name (col1,col2) VALUES(15,col1*2); ``` ```sql DELETE FROM table [ WHERE condition ] [ORDER BY ...] [LIMIT row_count] ``` ```sql UPDATE table SET col = expression [,...] [ FROM fromlist ] [ WHERE condition ] [ORDER BY ...] [LIMIT row_count] ``` **DCL（Data Control Language）语句：**数据控制语句，用于控制不同数据段直接的许可和访问级别的语句。这些语句定义了数据库、表、字段、用户的访问权限和安全级别。主要的语句关键字包括 grant、revoke 等。 ```sql GRANT priv_type [(column_list)] [, priv_type [(column_list)]] ... ON [object_type] priv_level TO user_or_role [, user_or_role] ... [WITH GRANT OPTION] GRANT PROXY ON user_or_role TO user_or_role [, user_or_role] ... [WITH GRANT OPTION] GRANT role [, role] ... TO user_or_role [, user_or_role] ... [WITH ADMIN OPTION] object_type: { TABLE | FUNCTION | PROCEDURE } priv_level: { | db_name.* | db_name.tbl_name | tbl_name | db_name.routine_name } user_or_role: { user | role } GRANT ALL ON db1.* TO 'jeffrey'@'localhost'; ``` 参考资料： SQL92 http://owen.sj.ca.us/rkowen/howto/sql92F.html MySql文档 https://dev.mysql.com/doc/refman/8.0/en/sql-syntax.html