让我们首先创建一个 -mysql> create table DemoTable1392 -> ( -> ArrivalDate date -> ); Query OK, 0 rows affected (0.43 sec)插入一些记录到表中使用 insert -mysql> insert into DemoTable1392 values('2019-09-10'); Query OK, 1 row affected (0.46 sec) mysql> insert into DemoTable1392 values('2019-09-26'); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable1392 values('2019-09-12'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1392 values('2018-09-20'); Query OK, 1 row affected (0.31 sec) mysql> insert into DemoTable1392 values('2019-10-11'); Query OK, 1 row affected (0.11 sec)显示表中所有记录使用 select ... 阅读更多

错误发生是因为我们在列名末尾有一个逗号，就在“from tablename”之前。这是您可能遇到的错误 -mysql> select ClientId, ClientName, ClientAge, from DemoTable1391; 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 'from DemoTable1391' at line 1要删除错误，如上所述，您需要从表中删除最后一个逗号。让我们首先创建一个 -mysql> create table DemoTable1391 -> ( -> ClientId int NOT ... 阅读更多

如果字符串以整数开头，则将其转换为整数，否则不会。让我们首先创建一个 -mysql> create table DemoTable1390 -> ( -> StudentId varchar(20) -> ); Query OK, 0 rows affected (0.93 sec)插入一些记录到表中使用 insert -mysql> insert into DemoTable1390 values('563_John'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1390 values('1001_Carol_Taylor'); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable1390 values('David_Miller_789'); Query OK, 1 row affected (0.07 sec) mysql> insert into DemoTable1390 values('456_AdamSmith'); Query OK, 1 row affected (0.11 sec)显示所有记录从 ... 阅读更多

让我们首先创建一个 -mysql> create table DemoTable1 -> ( -> StudentFirstName varchar(20), -> StudentLastName varchar(20), -> StudentAge int, -> StudentCountryName varchar(20) -> ); Query OK, 0 rows affected (4.20 sec)现在让我们将 MySQL 中所有列名转换为小写 -mysql> select concat('alter table ', table_name, ' change `', column_name, '` `', -> lower(column_name), '` ', column_type, ';') -> from information_schema.columns where table_schema = 'demo';这将产生以下输出 -+-----------------------------------------------------------------------------------------------------------------+ | concat('alter table ', table_name, ' change `', column_name, '` `', lower(column_name), '` ', column_type, ';') | +-----------------------------------------------------------------------------------------------------------------+ | ... 阅读更多

让我们首先创建一个 -mysql> create table DemoTable1620 -> ( -> Subject varchar(20) -> ); Query OK, 0 rows affected (0.42 sec)插入一些记录到表中使用 insert -mysql> insert into DemoTable1620 values('mysql'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1620 values('MySql'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1620 values('mYSQL'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable1620 values('MySQL'); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable1620 values('MYSQL'); Query OK, 1 row affected (0.20 sec)显示表中所有记录使用 select ... 阅读更多

为此，请使用连接概念。让我们首先创建一个 -mysql> create table DemoTable1389 -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentMarks int -> ); Query OK, 0 rows affected (2.73 sec)使用 insert 命令插入一些记录到表中。在这里，我们也插入了重复的值 -mysql> insert into DemoTable1389(StudentMarks) values(40); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable1389(StudentMarks) values(40); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable1389(StudentMarks) values(68); Query OK, 1 row affected (0.25 sec) mysql> insert into DemoTable1389(StudentMarks) values(78); Query OK, ... 阅读更多

以下是语法 -select * from yourViewName;让我们首先创建一个表 -mysql> create table DemoTable1388 -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(40) -> ); Query OK, 0 rows affected (0.71 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable1388(StudentName) values('Chris'); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable1388(StudentName) values('Bob'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable1388(StudentName) values('David'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1388(StudentName) values('Mike'); Query OK, 1 row affected (0.29 sec)显示所有 ... 阅读更多

要组合，请使用 GROUP_CONCAT() 函数将两行中的某些属性组合成一行。作为分隔符，使用连字符。让我们首先创建一个表 -mysql> create table DemoTable1386 -> ( -> Title varchar(255), -> Name varchar(60) -> ); 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 DemoTable1386 values('Introduction to MySQL', 'Paul DuBois'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1386 values('Java in Depth', 'Khalid Mughal'); Query OK, 1 row affected (0.48 sec) mysql> insert into DemoTable1386 values('Introduction to MySQL', 'Russell Dyer'); Query OK, ... 阅读更多

要在单个 MySQL 查询中获取多行，请使用 LIKE 运算符。让我们首先创建一个表 -mysql> create table DemoTable1385 -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(20) -> ); Query OK, 0 rows affected (0.90 sec)使用 insert 命令在表中插入一些记录 -mysql> insert into DemoTable1385(Name) values('Chris Brown'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1385(Name) values('Adam Smith'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable1385(Name) values('Carol Taylor'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable1385(Name) values('John ... 阅读更多

让我们首先创建一个表 -mysql> create table DemoTable1384 -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(20), -> StudentAge int -> ); Query OK, 0 rows affected (0.63 sec)使用 insert 命令在表中插入一些记录。在这里，我们在单个查询中插入多行 -mysql> insert into DemoTable1384(StudentName, StudentAge) values('Chris Brown', 21), ('David Miller', 22), -> ('Carol Taylor', 19), ('Adam Smith', 23); Query OK, 4 rows affected (0.11 sec) Records: 4 Duplicates: 0 Warnings: 0使用 select 语句显示表中的所有记录 -mysql> select * ... 阅读更多