让我们首先创建一个表 -mysql> create table DemoTable(    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    Name varchar(100) ); Query OK, 0 rows affected (0.47 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable(Name) values('John'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable(Name) values('Bob'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable(Name) values('Adam'); Query OK, 1 row affected (0.28 sec)使用 select 语句显示表中的所有记录 -mysql> select *from DemoTable;这将产生以下输出 -+----+------+ | Id | Name | +----+------+ | 1 | ... 阅读更多

如果某行匹配，则语句 SELECT TRUE 返回 1。让我们首先创建一个表 -mysql> create table DemoTable(Name varchar(100)); Query OK, 0 rows affected (0.54 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable values('Chris'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('Robert'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('David'); Query OK, 1 row affected (0.12 sec)使用 select 语句显示表中的所有记录 -mysql> select *from DemoTable;这将产生以下输出 -+--------+ | Name   | +--------+ | Chris  | | Robert ... 阅读更多

让我们首先创建一个表 -mysql> create table DemoTable(GetSundayDate date); Query OK, 0 rows affected (0.44 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable values('2019-08-07'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values('2018-09-05'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values('2019-09-12'); Query OK, 1 row affected (0.17 sec)使用 select 语句显示表中的所有记录 -mysql> select *from DemoTable;这将产生以下输出 -+---------------+ | GetSundayDate | +---------------+ | 2019-08-07    | | 2018-09-05    | | 2019-09-12    | +---------------+ 3 rows in ... 阅读更多

要将 varchar 转换为无符号整数，请使用 CAST() 函数。让我们首先创建一个表 -mysql> create table DemoTable868(Amount varchar(100)); Query OK, 0 rows affected (0.51 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable868 values('781'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable868 values('990'); Query OK, 1 row affected (0.25 sec) mysql> insert into DemoTable868 values('1002'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable868 values('560'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable868 values('890'); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable868 values('9890'); ... 阅读更多

为此，请使用 LIMIT 和 OFFSET。让我们首先创建一个表 -mysql> create table DemoTable867(EmployeeSalary int); Query OK, 0 rows affected (0.64 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable867 values(63737); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable867 values(899833); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable867 values(23644); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable867 values(89393); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable867 values(534333); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable867 values(889322); Query OK, 1 ... 阅读更多

为此，请使用 CASE 语句并为 SUM 和 SUBTRACTION 设置值。让我们首先创建一个表 -mysql> create table DemoTable866(    Status varchar(100),    Amount int ); Query OK, 0 rows affected (0.63 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable866 values('ACTIVE', 50); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable866 values('INACTIVE', 70); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable866 values('INACTIVE', 20); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable866 values('ACTIVE', 100); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable866 ... 阅读更多

让我们首先创建一个表 -mysql> create table DemoTable839(    StudentFirstName varchar(100),    StudentLastName varchar(100) ); Query OK, 0 rows affected (0.69 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable839 values('Chris', 'Brown'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable839 values('', 'Taylor'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable839 values(NULL, 'Taylor'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable839 values('Adam', 'Smith'); Query OK, 1 row affected (0.12 sec)使用 select 语句显示表中的所有记录 -mysql> select *from DemoTable839;这将产生以下 ... 阅读更多

SELECT(COLNAME) 表示我们正在为该列创建别名。让我们看一个示例并创建一个表 -mysql> create table DemoTable865(    FirstName varchar(100),    LastName varchar(100) ); Query OK, 0 rows affected (0.77 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable865 values('Chris', 'Brown'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable865 values('Adam', 'Smith'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable865 values('David', 'Miller'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable865 values('Carol', 'Taylor'); Query OK, 1 row affected (0.15 sec)显示所有记录 ... 阅读更多

为此，您可以使用 DATE()。让我们首先创建一个表 -mysql> create table DemoTable864(DueDateTime timestamp); Query OK, 0 rows affected (0.56 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable864 values('2019-01-10 12 −34 −55'); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable864 values('2016-12-11 11 −12 −00'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable864 values('2015-04-01 10 −00 −00'); Query OK, 1 row affected (0.28 sec) mysql> insert into DemoTable864 values('2017-05-20 04 −40 −10'); Query OK, 1 row affected (0.17 sec)显示表中的所有记录使用 select 语句 ... 阅读更多

为此，请使用 ENUM 数据类型。让我们首先创建一个表 -mysql> create table DemoTable838(Color ENUM('RED','GREEN','BLUE')); Query OK, 0 rows affected (0.67 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable838 values('RED'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable838 values('Green'); Query OK, 1 row affected (0.64 sec) mysql> insert into DemoTable838 values('Blue'); Query OK, 1 row affected (0.88 sec)使用 select 语句显示表中的所有记录 -mysql> select *from DemoTable838;这将产生以下输出 -+-------+ | Color | +-------+ | RED | | GREEN | | BLUE | +-------+ 3 rows in set (0.00 sec)