[Software testing] SQL statements commonly used in MySQL operation data tables (summary)

Contents: Guide

- foreword

foreword

What are the operations on the data table?

Create a data table;
view the table structure;
view the creation statement of the data table;
copy the data table;
modify the data table;
delete the data table;

Create data table

grammatical format

CREATE TABLE <表名> ( [表定义选项] )[表选项][分区选项];

Note:
Table name: two ways of writing, you can directly write the name of the data table tbl_name, or db_name.tbl_name, first specify the database and then specify the data table name; the latter way is to create a table under the specified database in this way, regardless of whether it is in the current database or not. Table definition options: generally composed of column names, column definitions, default values, constraints, and
indexes

example

# 创建数据表
CREATE TABLE yytest (
    id INT ( 10 ) NOT NULL UNIQUE PRIMARY KEY,
    uname VARCHAR ( 20 ) NOT NULL,
    sex VARCHAR ( 4 ),
    birth YEAR,
    department VARCHAR ( 20 ),
    address VARCHAR ( 50 ),
    yypolo VARCHAR ( 20 ) 
);

# 指定数据库，创建数据表
CREATE TABLE yytest.polotest (
    id INT ( 10 ) NOT NULL UNIQUE PRIMARY KEY AUTO_INCREMENT,
    stu_id INT ( 10 ) NOT NULL,
    c_name VARCHAR ( 20 ),
    istester VARCHAR ( 50 ),
    grade INT ( 10 ) 
);

View table structure

desc yytest.yytest;

General field display instructions:
Null: Indicates whether the field can store NULL values
Key: Indicates whether the field has been indexed. PRI indicates the primary key, UNI indicates the UNIQUE index, and MUL indicates that a given value is allowed to appear multiple times
Default: indicates whether the field has a default value, and if so, what is the value
Extra: indicates additional information about the field, such as AUTO_INCREMENT, etc.

View the creation statement of the data table

show create table yytest;

Not only can you view the detailed statement when creating the table, but you can also view the storage engine and character encoding

copy data table

# 仅复制表结构
create table yytest2 like yytest;

# 复制表结构和数据
create table yytest3 as select  * from yytest;

# 仅复制表的指定字段结构
create table yytest4 as select id,uname,sex from yytest where 1<>1;

# 复制表的指定字段结构和数据
create table yytest5 as select id,uname,sex from yytest;

# 查看表创建语句：没有包含主键和自增
show create table yytest5;

Note:
Only copy the structure of all fields and directly add like
copy table does not include primary key, index, auto-increment, etc.

modify data table

grammatical format

ALTER TABLE <表名> [修改操作];

Commonly used table modification operations

Modify table name;
modify field data type or field name;
add and delete fields;
modify the arrangement position of fields;
add, drop, change, modify, rename;

modify table name

grammatical format

ALTER TABLE <旧表名> RENAME [TO] <新表名>；

Note:
[TO] can be added or not, and the result will not be affected.
Modifying the table name will not affect the table structure

example

alter table yytest2 rename to yytest22;
alter table yytest22 rename yytest22;

Modify the order of fields

grammatical format

ALTER TABLE <表名> MODIFY <字段名> <数据类型> [FIRST|AFTER 已存在的字段名];

example

# 放在首位
alter table yytest22 modify sex int(2) first;

# 放在birth字段后面
alter table yytest22 modify sex int(2) after birth;

Modify field data type

grammatical format

ALTER TABLE <表名> MODIFY <字段名> <数据类型>;

example

# 修改字段数据类型
alter table yytest22 modify sex int(2);

modify field name

grammatical format

ALTER TABLE <表名> CHANGE <旧字段> <新字段> <数据类型>;

example

修改字段名
alter table yytest22 change sex sexs int(2);

# 修改字段数据类型和字段名
alter table yytest22 change sexs sex varchar(4);

Note:
change can not only change the field name, but also change the field data type

add field

grammatical format

ALTER TABLE <表名> ADD <字段名> <数据类型>  [约束条件] [FIRST|AFTER 已存在的字段名];

example

# 添加字段
alter table yytest22 add  phone varchar(11);

# 添加字段到首位
alter table yytest22 add  phone varchar(11) not null default 2 first;

# 添加字段到某个字段后面
alter table yytest22 add  phone varchar(11) after sex;

delete field

grammatical format

ALTER TABLE <表名> DROP <字段名>；

example

# 删除字段
alter table yytest22 drop  phone;

delete data table

grammatical format

DROP TABLE [IF EXISTS] 表名1 [ ,表名2, 表名3 ...]

You can see that it is almost the same as deleting the library

example

# 删除表如果存在
drop table if exists yytest,polotest

Be careful, the data will be cleared!

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