为此，使用 MySQL 的 MONTH() 和 YEAR() 方法。让我们先创建一个表：mysql> create table DemoTable1562 -> ( -> VoucherValue int, -> RechargeDate date -> ); Query OK, 0 rows affected (1.40 sec)使用 insert 命令插入一些记录：mysql> insert into DemoTable1562 values(149, '2019-10-21'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1562 values(199, '2019-10-13'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable1562 values(399, '2018-10-13'); Query OK, 1 row affected (0.25 sec) mysql> insert into DemoTable1562 values(450, '2019-10-13'); Query OK, 1 row affected (0.20 sec)显示所有… 阅读更多

为此，您可以使用子查询和 MIN()。让我们先创建一个表：mysql> create table DemoTable -> ( -> Name varchar(20), -> Score int -> ); Query OK, 0 rows affected (0.56 sec)使用 insert 命令插入一些记录：mysql> insert into DemoTable values('John', 56); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('John', 45); Query OK, 1 row affected (0.24 sec) mysql> insert into DemoTable values('John', 58); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('Chris', 43); Query OK, 1 row affected (0.15 ... 阅读更多

为此，您可以使用 GROUP_CONCAT()。让我们先创建一个表：mysql> create table DemoTable1561 -> ( -> StudentName varchar(20), -> Title text -> ); Query OK, 0 rows affected (0.60 sec)使用 insert 命令插入一些记录：mysql> insert into DemoTable1561 values('Adam', 'Learning Java'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable1561 values('Bob', 'Learning C'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1561 values('Adam', 'Learning Spring and Hibernate Framework'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable1561 values('Carol', 'Learning MySQL from basic'); Query ... 阅读更多

为了获得相同的结果，不要使用 ! 运算符。MySQL 已经提供了 NOT 关键字。让我们先创建一个表：mysql> create table DemoTable1560 -> ( -> Value1 int -> ); Query OK, 0 rows affected (0.50 sec)使用 insert 命令插入一些记录：mysql> insert into DemoTable1560 values(0); Query OK, 1 row affected (0.16 sec)使用 select 语句显示表中的所有记录：mysql> select * from DemoTable1560;这将产生以下输出：+--------+ | Value1 | +--------+ | 0 | +--------+ 1 row in set (0.00 sec)以下是… 阅读更多

您不能使用 index 作为列名，因为它是一个保留字。为此，您需要在列名周围使用反引号。如果您使用保留字作为列名，您会看到以下错误：mysql> create table DemoTable -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> index int -> )ENGINE=MyISAM; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'int )ENGINE=MyISAM' at line 4让我们先… 阅读更多

要随机排序查询结果，请使用 ORDER BY RAND()。语法如下：select * from DemoTable1559 where yourColumnName IN(yourValue1, yourValue2, ....N) order by rand() limit yourLimitValue;让我们先创建一个表：mysql> create table DemoTable1559 -> ( -> EmployeeId int, -> EmployeeName varchar(20), -> EmployeeAge int -> ); Query OK, 0 rows affected (1.22 sec)使用 insert 命令插入一些记录：mysql> insert into DemoTable1559 values(101, 'Bob', 28); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable1559 values(102, 'Robert', 26); Query OK, 1 row affected (0.16 sec) ... 阅读更多

要在 MySQL 中重新格式化日期时间，您可以使用 DATE_FORMAT()。MySQL 的默认格式为 yyyy-mm-dd。让我们先创建一个表：mysql> create table DemoTable1558 -> ( -> EmployeeJoiningDate datetime -> ); Query OK, 0 rows affected (1.10 sec)使用 insert 命令插入一些记录：mysql> insert into DemoTable1558 values(CURDATE()); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable1558 values(NOW()); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1558 values('2018-01-10'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable1558 values('2017-12-31'); Query OK, 1 row affected (0.18 sec)显示所有记录… 阅读更多

要打乱元素，您需要使用 ORDER BY RAND()。让我们先创建一个表：mysql> create table DemoTable1557 -> ( -> SubjectId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> SubjectName varchar(20) -> ); Query OK, 0 rows affected (0.91 sec)使用 insert 命令插入一些记录：mysql> insert into DemoTable1557(SubjectName) values('MySQL'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1557(SubjectName) values('MongoDB'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1557(SubjectName) values('Java'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1557(SubjectName) values('C'); Query OK, 1 row affected ... 阅读更多

让我们先创建一个表：mysql> create table DemoTable1 -> ( -> Id int, -> FirstName varchar(20) -> ); Query OK, 0 rows affected (0.52 sec)以下是创建第二个表的查询：mysql> create table DemoTable2 -> ( -> EmployeeId int, -> EmployeeName varchar(20) -> ); Query OK, 0 rows affected (0.51 sec)现在让我们创建一个触发器，以便在插入命令中更新 MySQL 表：mysql> DELIMITER // mysql> CREATE TRIGGER updateDemoOnInsert -> AFTER INSERT ON DemoTable2 -> FOR EACH ... 阅读更多

使用 FULLTEXT 搜索来快速搜索字符串。让我们先创建一个表：mysql> create table DemoTable1554 -> ( -> Title text -> ); Query OK, 0 rows affected (0.63 sec)以下是创建全文搜索的查询：mysql> create fulltext index faster_title on DemoTable1554(Title); Query OK, 0 rows affected, 1 warning (7.09 sec) Records: 0 Duplicates: 0 Warnings: 1使用 insert 命令插入一些记录：mysql> insert into DemoTable1554 values('John is working on MySQL database'); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable1554 values('Adam Smith is working on ... 阅读更多