让我们先创建一个表 - mysql> create table DemoTable1946    (    ShippingDate date    ); Query OK, 0 rows affected (0.00 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable1946 values('2019-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2018-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2017-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2019-04-22'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2019-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2015-12-11'); Query OK, 1 ... 阅读更多

要插入来自多个表中的记录，请使用 INSERT INTO SELECT 语句。在这里，我们将插入来自 2 个表中的记录。让我们先创建一个表 - mysql> create table DemoTable1943    (    Name varchar(20)    ); Query OK, 0 rows affected (0.00 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable1943 values('Chris'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1943 values('Robert'); Query OK, 1 row affected (0.00 sec)使用 select 语句显示表中的所有记录 - mysql> select * from DemoTable1943;这将产生以下输出 -+--------+ | Name   | +--------+ | Chris ... 阅读更多

为此，请使用正则表达式。语法如下 - select * from information_schema.schemata WHERE SCHEMA_NAME REGEXP '^yourValue_+[A-Z]';让我们创建一些数据库 - mysql> create database bank_APP1; Query OK, 1 row affected (0.00 sec) mysql> create database bank_APP2; Query OK, 1 row affected (0.00 sec) mysql> create database bank_APP3; Query OK, 1 row affected (0.00 sec)以下是获取名称中某个单词后包含大写字符的所有数据库的查询 - mysql> select * from information_schema.schemata    WHERE SCHEMA_NAME REGEXP '^bank_+[A-Z]';这将产生以下输出 -+--------------+-------------+----------------------------+------------------------+----------+ | CATALOG_NAME | SCHEMA_NAME | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH | +--------------+-------------+----------------------------+------------------------+----------+ | def   ... 阅读更多

为此，请使用 COUNT(*) 以及 GROUP BY 子句。让我们先创建一个表 - mysql> create table DemoTable1942    (    Value int    ); Query OK, 0 rows affected (0.00 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable1942 values(1); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1942 values(2); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1942 values(3); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1942 values(2); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1942 values(3); Query OK, 1 row affected (0.00 ... 阅读更多

要返回计数最高的字段，请使用 ORDER BY COUNT(*)。让我们先创建一个表 - mysql> create table DemoTable1940    (    FirstName varchar(20)    ); Query OK, 0 rows affected (0.00 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable1940 values('Chris'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1940 values('Mike'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1940 values('Adam'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1940 values('Mike'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1940 values('Chris'); Query OK, 1 row ... 阅读更多

为此，您可以使用 LEFT()。让我们先创建一个表 - mysql> create table DemoTable1939    (    FullName varchar(20)    ); Query OK, 0 rows affected (0.00 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable1939 values('Adam Smith'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1939 values('Robert Downey, Jr.'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1939 values('Sylvester Stallone'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1939 values('Chris Hemsworth'); Query OK, 1 row affected (0.00 sec)使用 select 语句显示表中的所有记录 - mysql> ... 阅读更多

要显示所有字段，请设置数据库为 table_schema，并将特定表设置为 table_name，如以下语法所示 - select column_name as anyAliasName from information_schema.columns    where table_schema=database()    and table_name=’yourTableName’\G让我们先创建一个表 - mysql> create table DemoTable1938    (    StudentId int,    StudentName varchar(20),    StudentAge int,    StudentCountryName varchar(20),    StudentMobileNumber bigint    ); Query OK, 0 rows affected (0.00 sec)以下是显示表所有字段的查询 - mysql> select column_name as ALL_FIELDS from information_schema.columns    where table_schema=database()    and table_name='DemoTable1938'\G这将产生以下输出 -*************************** 1. row *************************** ALL_FIELDS: StudentId ... 阅读更多

为此，请使用 CASE 语句与 ORDER BY 结合使用。让我们先创建一个表 - mysql> create table DemoTable1937    (    Name varchar(20)    ); Query OK, 0 rows affected (0.00 sec)使用 insert 命令在表中插入一些记录 - mysql> insert into DemoTable1937 values('Chris'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1937 values(NULL); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1937 values('Adam'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1937 values('John'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1937 values(''); Query OK, 1 row affected (0.00 sec) ... 阅读更多

要执行多个插入操作，语法如下：insert into yourTableName(yourColumnName1, yourColumnName2, yourColumnName3, ..N)    select yourValue1 as yourColumnName1, yourValue2 as yourColumnName2, yourValue3 as yourColumnName3, ......N    union    select yourValue1 as yourColumnName1, yourValue2 as yourColumnName2, yourValue3 as yourColumnName3, ......N . . N为了理解上述语法，让我们创建一个表：mysql> create table DemoTable1936    (    StudentId int,    StudentName varchar(20),    StudentCountryName varchar(20)    ); Query OK, 0 rows affected (0.00 sec)使用insert命令在表中插入一些记录：mysql> insert into DemoTable1936(StudentId, StudentName, StudentCountryName)    select 1001 as StudentId, 'Chris' as StudentName, 'US' ... 阅读更多

为此，使用 RLIKE 并按以下语法过滤记录 &Minus;select * from yourTableName    where yourColumnName rlike 'yourValue1|yourValue2';让我们首先创建一个表：mysql> create table DemoTable1935    (    Subject varchar(20)    ); Query OK, 0 rows affected (0.00 sec)使用 insert 命令在表中插入一些记录：mysql> insert into DemoTable1935 values('MySQL'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1935 values('Python'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1935 values('MongoDB'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1935 values('SQL Server'); Query OK, 1 row affected (0.00 ... 阅读更多