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MySQL 教程

MySQL 主页 MySQL 简介 MySQL RDBMS

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MySQL 数据类型 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

MySQL 示例

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MySQL LEFT() 函数

❮ MySQL 函数

示例

从字符串中提取 3 个字符（从左侧开始）

SELECT LEFT("SQL Tutorial", 3) AS ExtractString;
自己试试 »

定义和用法

LEFT() 函数从字符串中提取一定数量的字符（从左侧开始）。

提示： 也看看 RIGHT() 函数。

语法

LEFT(string, number_of_chars)

参数值

参数 描述
string 必需。要从中提取的字符串
number_of_chars 必需。要提取的字符数。如果此参数大于string中的字符数，此函数将返回string

技术细节

适用版本 从 MySQL 4.0 开始

更多示例

示例

从 "CustomerName" 列中的文本中提取 5 个字符（从左侧开始）

SELECT LEFT(CustomerName, 5) AS ExtractString
FROM Customers;
自己试试 »

❮ MySQL 函数

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