**SQL 分類：** **SQL 語句主要可以劃分為以下 4 個類別。** **DDL（Data Definition Languages）語句：**數據定義語言，這些語句定義了不同的數據段、數據庫、表、列、索引等數據庫對象的定義。常用的語句關鍵字主要包括 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 ）數據查詢語言，select語句。** ```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）語句：**數據操縱語句，用于添加、刪除、更新和查詢數據庫記錄，并檢查數據完整性，常用的語句關鍵字主要包括 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）語句：**數據控制語句，用于控制不同數據段直接的許可和訪問級別的語句。這些語句定義了數據庫、表、字段、用戶的訪問權限和安全級別。主要的語句關鍵字包括 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'; ``` 參考資料： SQL92 http://owen.sj.ca.us/rkowen/howto/sql92F.html MySql文檔 https://dev.mysql.com/doc/refman/8.0/en/sql-syntax.html