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SQL 教程

SQL 主页 SQL 简介 SQL 语法 SQL 选择 SQL 选择 Distinct SQL Where SQL 排序 SQL And SQL Or SQL Not SQL 插入 SQL Null 值 SQL 更新 SQL 删除 SQL 选择 Top SQL 聚合函数 SQL Min 和 Max SQL 计数 SQL 求和 SQL 平均值 SQL Like SQL 通配符 SQL In SQL Between SQL 别名 SQL 联接 SQL 内联接 SQL 左联接 SQL 右联接 SQL 全联接 SQL 自联接 SQL Union SQL 分组 SQL Having SQL Exists SQL Any, All SQL 选择 Into SQL 插入 Into 选择 SQL Case SQL Null 函数 SQL 存储过程 SQL 注释 SQL 运算符

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SQL 参考资料

SQL 关键字
ADD ADD CONSTRAINT ALL ALTER ALTER COLUMN ALTER TABLE AND ANY AS ASC BACKUP DATABASE BETWEEN CASE CHECK COLUMN CONSTRAINT CREATE CREATE DATABASE CREATE INDEX CREATE OR REPLACE VIEW CREATE TABLE CREATE PROCEDURE CREATE UNIQUE INDEX CREATE VIEW DATABASE DEFAULT DELETE DESC DISTINCT DROP DROP COLUMN DROP CONSTRAINT DROP DATABASE DROP DEFAULT DROP INDEX DROP TABLE DROP VIEW EXEC EXISTS FOREIGN KEY FROM FULL OUTER JOIN GROUP BY HAVING IN INDEX INNER JOIN INSERT INTO INSERT INTO SELECT IS NULL IS NOT NULL JOIN LEFT JOIN LIKE LIMIT NOT NOT NULL OR ORDER BY OUTER JOIN PRIMARY KEY PROCEDURE RIGHT JOIN ROWNUM SELECT SELECT DISTINCT SELECT INTO SELECT TOP SET TABLE TOP TRUNCATE TABLE UNION UNION ALL UNIQUE UPDATE VALUES VIEW WHERE
MySQL 函数
字符串函数: ASCII CHAR_LENGTH CHARACTER_LENGTH CONCAT CONCAT_WS FIELD FIND_IN_SET FORMAT INSERT INSTR LCASE LEFT LENGTH LOCATE LOWER LPAD LTRIM MID POSITION REPEAT REPLACE REVERSE RIGHT RPAD RTRIM SPACE STRCMP SUBSTR SUBSTRING SUBSTRING_INDEX TRIM UCASE UPPER 数值函数: ABS ACOS ASIN ATAN ATAN2 AVG CEIL CEILING COS COT COUNT DEGREES DIV EXP FLOOR GREATEST LEAST LN LOG LOG10 LOG2 MAX MIN MOD PI POW POWER RADIANS RAND ROUND SIGN SIN SQRT SUM TAN TRUNCATE 日期函数: ADDDATE ADDTIME CURDATE CURRENT_DATE CURRENT_TIME CURRENT_TIMESTAMP CURTIME DATE DATEDIFF DATE_ADD DATE_FORMAT DATE_SUB DAY DAYNAME DAYOFMONTH DAYOFWEEK DAYOFYEAR EXTRACT FROM_DAYS HOUR LAST_DAY LOCALTIME LOCALTIMESTAMP MAKEDATE MAKETIME MICROSECOND MINUTE MONTH MONTHNAME NOW PERIOD_ADD PERIOD_DIFF QUARTER SECOND SEC_TO_TIME STR_TO_DATE SUBDATE SUBTIME SYSDATE TIME TIME_FORMAT TIME_TO_SEC TIMEDIFF TIMESTAMP TO_DAYS WEEK WEEKDAY WEEKOFYEAR YEAR YEARWEEK 高级函数: BIN BINARY CASE CAST COALESCE CONNECTION_ID CONV CONVERT CURRENT_USER DATABASE IF IFNULL ISNULL LAST_INSERT_ID NULLIF SESSION_USER SYSTEM_USER USER VERSION
SQL Server 函数
字符串函数: ASCII CHAR CHARINDEX CONCAT 使用 + 连接 CONCAT_WS DATALENGTH DIFFERENCE FORMAT LEFT LEN LOWER LTRIM NCHAR PATINDEX QUOTENAME REPLACE REPLICATE REVERSE RIGHT RTRIM SOUNDEX SPACE STR STUFF SUBSTRING TRANSLATE TRIM UNICODE UPPER 数值函数: ABS ACOS ASIN ATAN ATN2 AVG CEILING COUNT COS COT DEGREES EXP FLOOR LOG LOG10 MAX MIN PI POWER RADIANS RAND ROUND SIGN SIN SQRT SQUARE SUM TAN 日期函数: CURRENT_TIMESTAMP DATEADD DATEDIFF DATEFROMPARTS DATENAME DATEPART DAY GETDATE GETUTCDATE ISDATE MONTH SYSDATETIME YEAR 高级函数 CAST COALESCE CONVERT CURRENT_USER IIF ISNULL ISNUMERIC NULLIF SESSION_USER SESSIONPROPERTY SYSTEM_USER USER_NAME
MS Access 函数
字符串函数: Asc Chr Concat with & CurDir Format InStr InstrRev LCase Left Len LTrim Mid Replace Right RTrim Space Split Str StrComp StrConv StrReverse Trim UCase 数值函数: Abs Atn Avg Cos Count Exp Fix Format Int Max Min Randomize Rnd Round Sgn Sqr Sum Val 日期函数: Date DateAdd DateDiff DatePart DateSerial DateValue Day Format Hour Minute Month MonthName Now Second Time TimeSerial TimeValue Weekday WeekdayName Year 其他函数: CurrentUser Environ IsDate IsNull IsNumeric
SQL 快速参考

SQL 示例

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SQL DELETE 语句

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SQL DELETE 语句

The DELETE 语句用于删除表中的现有记录。

DELETE 语法

DELETE FROM table_name WHERE condition;

注意: 在删除表中的记录时要小心！请注意 WHERE 子句在 DELETE 语句中。The WHERE 子句指定要删除的记录。如果您省略 WHERE 子句，则将删除表中的所有记录！

演示数据库

下面是示例中使用的 Customers 表的选择

CustomerID CustomerName ContactName Address City PostalCode Country
1

 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany
2 Ana Trujillo Emparedados y helados Ana Trujillo Avda. de la Constitución 2222 México D.F. 05021 Mexico
3 Antonio Moreno Taquería Antonio Moreno Mataderos 2312 México D.F. 05023 Mexico
4

 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden

SQL DELETE 示例

以下 SQL 语句从 "Customers" 表中删除客户 "Alfreds Futterkiste"

示例

DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste';

"Customers" 表现在将显示如下

CustomerID CustomerName ContactName Address City PostalCode Country
2 Ana Trujillo Emparedados y helados Ana Trujillo Avda. de la Constitución 2222 México D.F. 05021 Mexico
3 Antonio Moreno Taquería Antonio Moreno Mataderos 2312 México D.F. 05023 Mexico
4

 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden

删除所有记录

可以删除表中的所有行，而不会删除该表。这意味着表结构、属性和索引将保持不变

DELETE FROM table_name;

以下 SQL 语句将删除 "Customers" 表中的所有行，而不会删除该表

示例

DELETE FROM Customers;

删除表

要完全删除该表，请使用 DROP TABLE 语句

示例

删除 Customers 表

DROP TABLE Customers;

通过练习测试自己

练习

从 Customers 表中删除所有 Country 值为 'Norway' 的记录。

 Customers
 Country = 'Norway';

开始练习

视频: SQL DELETE 语句

SQL Tutorial on YouTube
SQL Tutorial on YouTube


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