让我们首先创建一个表 - mysql> create table DemoTable (    FirstName varchar(100) ); Query OK, 0 rows affected (0.65 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 (0.09 sec) mysql> insert into DemoTable values('Robert'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values('Mike'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('Sam'); Query OK, 1 row affected (0.10 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 ... 阅读更多

要仅从字符串值中返回前 15 个字符，请使用 MySQL SUBSTR() 函数。让我们首先创建一个表 - mysql> create table DemoTable (    Title 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 DemoTable values('Introduction to MySQL'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values('Introduction to Java'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('C in Depth with data structure and algorithm'); Query OK, 1 row affected (0.15 sec)使用 select 语句显示表中的所有记录 - mysql> ... 阅读更多

要添加百分号符号，请使用 CONCAT() 函数。让我们首先创建一个表 - mysql> create table DemoTable (    StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,    StudentName varchar(100),    StudentScore int ); Query OK, 0 rows affected (0.68 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable(StudentName, StudentScore) values('John', 65); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable(StudentName, StudentScore) values('Chris', 98); Query OK, 1 row affected (0.30 sec) mysql> insert into DemoTable(StudentName, StudentScore) values('Robert', 91); Query OK, 1 row affected (0.09 sec)使用 select 语句显示表中的所有记录 - mysql> ... 阅读更多

要添加前导零，可以使用 LPAD()。让我们首先创建一个表 - mysql> create table DemoTable (    Code varchar(100) ); Query OK, 0 rows affected (0.87 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable values('JS'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('CB'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values('DM'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('CT'); Query OK, 1 row affected (0.07 sec)使用 select 语句显示表中的所有记录 - mysql> select *from DemoTable;这将产生 ... 阅读更多

为此，您可以使用 DATE() 函数。让我们首先创建一个表 - mysql> create table DemoTable (    Number int ); Query OK, 0 rows affected (0.48 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable values(20190108); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values(20161231); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(20170411); Query OK, 1 row affected (0.09 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 - +----------+ | Number   | +----------+ | 20190108 | ... 阅读更多

让我们首先创建一个表 - mysql> create table DemoTable (    Number int ); Query OK, 0 rows affected (0.79 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable values(56); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(78); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values(89); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(98); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable values(91); Query OK, 1 row affected (0.35 sec) mysql> insert into DemoTable values(96); Query OK, 1 row affected ... 阅读更多

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 (0.55 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable(Name) values('John Smith'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(Name) values('Carol Taylor'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(Name) values('John Doe'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(Name) values('Chris Brown'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(Name) values('John Brown'); Query OK, 1 row ... 阅读更多

让我们首先创建一个表 - mysql> create table DemoTable (    Download varchar(100) ); Query OK, 0 rows affected (0.53 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable values('120 Gigabytes'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('190 Gigabytes'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('250 Gigabytes'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('1000 Gigabytes'); 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 - +----------------+ ... 阅读更多

要从列表中获取特定的 varchar ID，可以使用 FIND_IN_SET()。让我们首先创建一个表 - mysql> create table DemoTable (    Id varchar(255) ); 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 DemoTable values('10, 100, 1000'); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable values('101, 120, 2'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('3, 4, 5'); Query OK, 1 row affected (0.11 sec)使用 select 语句显示表中的所有记录 - mysql> select *from DemoTable;这将产生 ... 阅读更多

为此，您可以使用 IS NULL 属性。让我们首先创建一个表 - mysql> create table DemoTable (    ProductPrice int,    ProductQuantity int,    TotalAmount int ); Query OK, 0 rows affected (1.22 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable(ProductPrice, ProductQuantity) values(100, 2); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(ProductPrice, ProductQuantity) values(500, 4); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable(ProductPrice, ProductQuantity) values(1000, 10); Query OK, 1 row affected (0.21 sec)使用 select 语句显示表中的所有记录 - mysql> select *from DemoTable;这将产生 ... 阅读更多