What are the commonly used SQL statements in software testing?

Catalog

1、 Data definition language

2、 Data operation language

3、 Data query language

4、 Data control language

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1、 Data definition language

DDL：Data Definition Language

One 、 Operation Library ：

--  Create a library 
create database db1;
--  Create whether the library exists , Create if it does not exist 
create database if not exists db1;
--  View all databases 
show databases;
--  View the definition information of a database  
show create database db1; 
--  Modify database character information 
alter database db1 character set utf8; 
--  Delete database 
drop database db1;

Two 、 Operation table ：

-- Create table 
create table student(
    id int,
    name varchar(32),
    age int,
    score double(4,1),
    birthday date,
    insert_time timestamp
);
--  View table structure 
desc  Table name ;
--  View the SQL sentence 
show create table  Table name ;
--  Modify the name of the table 
alter table  Table name  rename to New table name ;
--  Add a column 
alter table  Table name  add  Name   data type ;
--  Delete column 
alter table  Table name  drop  Name ;
--  Delete table 
drop table  Table name ;
drop table if exists  Table name  ;

        

 

2、 Data operation language

DML：Data Manipulation Language

One 、 increase insert into：

--  Write all the names 
insert into  Table name ( Name 1, Name 2,... Name n) values( value 1, value 2,... value n);
--  No listing （ Add all columns ）
insert into  Table name  values( value 1, value 2,... value n);
--  Insert partial data 
insert into  Table name ( Name 1, Name 2) values( value 1, value 2);

Two 、 Delete delete：

--  Delete data in table 

delete from  Table name  where  Name  =  value ;


--  Delete all data in the table 

delete from  Table name ;

--  Delete all data in the table （ Efficient   Delete the table first , Then create the same table .）

truncate table  Table name ;

3、 ... and 、 modify update：

--  Modification without conditions ( All lines will be modified )

update  Table name  set  Name  =  value ;

--  Conditional modification 

updata  Table name  set  Name  =  value  where  Name  =  value ;

3、 Data query language

DQL：Data Query Language
There's a lot about query statements , Here we will not introduce the basic . This paper mainly introduces Sort query 、 Aggregate functions 、 Fuzzy query 、 Group query 、 Paging query 、 Internal connection 、 External connection 、 Subquery

One 、 Basic keywords ：

• BETWEEN...AND（ Between what ） and  IN( aggregate )

• --  Query age is greater than or equal to 20  Less than or equal to 30                
  SELECT * FROM student WHERE age >= 20 &&  age <=30;
  SELECT * FROM student WHERE age >= 20 AND  age <=30;
  SELECT * FROM student WHERE age BETWEEN 20 AND30;             
  --  Check age 22 year ,18 year ,25 Age information 
  SELECT * FROM student WHERE age = 22 OR age = 18 OR age = 25
  SELECT * FROM student WHERE age IN (22,18,25);

  is null( Not for null value ) And like（ Fuzzy query ）、distinct（ Remove duplicate values ）

--  The English score is not null
SELECT* FROM student WHERE english  IS NOT NULL;

 _: Any single character 
 %： More than one arbitrary character 
--  Find out what's the name of Ma ？like
SELECT * FROM student WHERE NAME LIKE ' Horse %';
--  The second word for a name is the person who changed             
SELECT * FROM student WHERE NAME LIKE "_ turn %";                
--  The search name is 3 One word man 
SELECT * FROM student WHERE NAME LIKE '___';                    
--  Search for the person whose name contains De 
SELECT * FROM student WHERE NAME LIKE '% Virtue %';
--  key word  DISTINCT  Used to return a unique different value .
--  grammar ：SELECT DISTINCT  Column name  FROM  The name of the table 
SELECT DISTINCT NAME FROM  student ;

Two 、 Sort query order by
grammar ：order by Clause

order by  Sort field 1  sort order 1 , Sort field 2  sort order 2...

Be careful ： If there are multiple sorting conditions , When the condition value of the current edge is the same , To judge the second condition .

--  Example 
SELECT *FROM person ORDER BY math; -- Default ascending order 
SELECT * FROM person ORDER BY math desc; -- Descending 

3、 ... and 、 Aggregate functions ： Take a column of data as a whole , Do the longitudinal calculation .

• count： Calculate the number of
• max： Calculate the maximum
• min： Calculate the minimum
• sum： The calculation and
• avg： Calculate the average

Four 、 Group query grout by
grammar ：group by Grouping field ;
Be careful ： Fields to be queried after grouping ： Grouping field 、 Aggregate functions

--  Group by sex . Check the men separately 、 The average score of female students 
SELECT sex , AVG(math) FROM student GROUP BY sex;
 
--  Group by sex . Check the men separately 、 The average score of female students , The number of 
SELECT sex , AVG(math),COUNT(id) FROM student GROUP BY sex;
 
--   Group by sex . Check the men separately 、 The average score of female students , The number of   requirement ： The score is below 70 Divided people , Don't participate in grouping 
SELECT sex , AVG(math),COUNT(id) FROM student WHERE math > 70 GROUP BY sex;
 
 --   Group by sex . Check the men separately 、 The average score of female students , The number of   requirement ： The score is below 70 Divided people , Don't participate in grouping , After grouping . There are more people than 2 personal 
SELECT sex , AVG(math),COUNT(id) FROM student WHERE math > 70 GROUP BY sex HAVING COUNT(id) > 2;
SELECT sex , AVG(math),COUNT(id)  The number of  FROM student WHERE math > 70 GROUP BY sex HAVING  The number of  > 2;

5、 ... and 、 Paging query ：

grammar ：limit Index started , Number of queries per page ;

The formula ： Index started = （ The current page number - 1） * Number of entries per page

limit It's a MySQL" dialect "

--  Each page shows 3 Bar record 
SELECT * FROM student LIMIT 0,3; --  The first 1 page 
SELECT * FROM student LIMIT 3,3; --  The first 2 page 
SELECT * FROM student LIMIT 6,3; --  The first 3 page 

                         

 

6、 ... and 、 Internal connection query ：

• From which tables to query data
• What are the conditions
• Which fields to query

1. Implicit inner join ： Use where Conditions eliminate useless data

--  Query the name of the employee table , Gender . The name of the Department table 
SELECT emp.name,emp.gender,dept.name FROM emp,dept WHERE emp.`dept_id` = dept.`id`;
     
SELECT 
    t1.name, --  The name of the employee form 
    t1.gender,--  The gender of the employee table 
    t2.name --  The name of the Department table 
FROM
    emp t1,
    dept t2
WHERE 
    t1.`dept_id` = t2.`id`;

2. Explicit inner connection

--  grammar ：
select  Field list  from  Table name 1 [inner] join  Table name 2 on  Conditions 
--  for example ：
SELECT * FROM emp INNER JOIN dept ON emp.`dept_id` = dept.`id`;   
SELECT * FROM emp JOIN dept ON emp.`dept_id` = dept.`id`;

7、 ... and 、 External connection query

1. The left outer join -- It queries all the data in the left table and its intersection part .

--  grammar ：
select  Field list  from  surface 1 left [outer] join  surface 2 on  Conditions ;
--  Example ：
--  Query all employee information , If the employee has a department , Then query the Department name , There is no department , The Department name is not displayed 
SELECT  t1.*,t2.`name` FROM emp t1 LEFT JOIN dept t2 ON t1.`dept_id` = t2.`id`;

2. Right connection  -- It queries all the data in the right table and its intersection part .

--  grammar ：
select  Field list  from  surface 1 right [outer] join  surface 2 on  Conditions ;
--  Example ：
SELECT  * FROM dept t2 RIGHT JOIN emp t1 ON t1.`dept_id` = t2.`id`;

8、 ... and 、 Subquery ： Nested query in query

--  Query the highest paid employee information 
-- 1  Find out what the maximum wage is  9000
SELECT MAX (salary) FROM emp;

-- 2  Query employee information , And the salary is equal to 9000 Of 
SELECT * FROM emp WHERE emp.`salary` = 9000;

--  One sql Just do it . This is the subquery 
SELECT * FROM emp WHERE emp.`salary` = (SELECT MAX(salary) FROM emp);

1. The result of subquery is single row and single column ：

Subqueries can be used as conditions , Use operators to judge . Operator ：> >= < <= =

--  Query people whose wages are less than the average 
SELECT * FROM emp WHERE emp.salary < (SELECT AVG(salary) FROM emp);

2. The result of subquery is multi row and single column ：

Subqueries can be used as conditions , Use the operator in To judge

--  Inquire about ' Finance Department ' and ' The Marketing Department ' All employee information 
SELECT id FROM dept WHERE NAME = ' Finance Department ' OR NAME = ' The Marketing Department ';
SELECT * FROM emp WHERE dept_id = 3 OR dept_id = 2;
     
--  Subquery 
SELECT * FROM emp WHERE dept_id IN (SELECT id FROM dept WHERE NAME = ' Finance Department ' OR NAME = ' The Marketing Department ');

3. The result of subquery is multi row and multi column ：

Subquery can participate in query as a virtual table

--  Query the entry date of the employee 2011-11-11 Future employee information and department information 
--  Subquery 
SELECT * FROM dept t1 ,(SELECT * FROM emp WHERE emp.`join_date` > '2011-11-11') t2 WHERE t1.id = t2.dept_id;

--  Common internal connection 
SELECT * FROM emp t1,dept t2 WHERE t1.`dept_id` = t2.`id` AND t1.`join_date` >  '2011-11-11'

4、 Data control language

DCL：Data Control Language

One 、 Manage users

• Add users

 grammar ：CREATE USER ' user name '@' Host name ' IDENTIFIED BY ' password ';

Delete user

 grammar ：DROP USER ' user name '@' Host name ';

Two 、 Rights management

• Query authority

--  Query authority 
SHOW GRANTS FOR ' user name '@' Host name ';
SHOW GRANTS FOR 'lisi'@'%';

Grant authority

--  Grant authority 
grant  Permission list  on  Database name . Table name  to ' user name '@' Host name '; 
--  Give all permissions to Zhang San , On any table in any database 
GRANT ALL ON *.* TO 'zhangsan'@'localhost';

Revoke authority

--  Revoke authority ：
revoke  Permission list  on  Database name . Table name  from ' user name '@' Host name ';
REVOKE UPDATE ON db3.`account` FROM 'lisi'@'%';.