Some basic database operations (providing the original database information)

Database creation file used
Create method ：cmd The window opens mysql after source:sql File path Create database

create database if not exists db1 default charset utf8;
USE db1;
--  Departmental table 
CREATE TABLE DEPT(
	DEPTNO INT PRIMARY KEY,
	DNAME VARCHAR(14), --  Department name 
	LOC VARCHAR(13)--  Department Address 
)CHARSET=UTF8,ENGINE=INNODB;	
INSERT INTO DEPT VALUES	(10,'ACCOUNTING','NEW YORK');
INSERT INTO DEPT VALUES (20,'RESEARCH','DALLAS');
INSERT INTO DEPT VALUES	(30,'SALES','CHICAGO');
INSERT INTO DEPT VALUES	(40,'OPERATIONS','BOSTON');

--  The employee table 
CREATE TABLE EMP(
	EMPNO INT  PRIMARY KEY, --  Employee number 
	ENAME VARCHAR(10), --  Employee name 
	JOB VARCHAR(9), --  Staff work 
	MGR INT, --  Employee's direct leader No 
	HIREDATE DATE, --  Entry time 
	SAL DOUBLE, --  Wages 
	COMM DOUBLE, --  Bonus 
	DEPTNO INT  --  Department 
);  --  relation dept surface  
INSERT INTO EMP VALUES(7369,'SMITH','CLERK',7566,"1980-12-17",800,NULL,20);
INSERT INTO EMP VALUES(7499,'ALLEN','SALESMAN',7698,'1981-02-20',1600,300,30);
INSERT INTO EMP VALUES(7521,'WARD','SALESMAN',7698,'1981-02-22',1250,500,30);
INSERT INTO EMP VALUES(7566,'JONES','MANAGER',7839,'1981-04-02',2975,NULL,20);
INSERT INTO EMP VALUES(7654,'MARTIN','SALESMAN',7698,'1981-09-28',1250,1400,30);
INSERT INTO EMP VALUES(7698,'BLAKE','MANAGER',7839,'1981-05-01',2850,NULL,30);
INSERT INTO EMP VALUES(7782,'CLARK','MANAGER',7839,'1981-06-09',2450,NULL,10);
INSERT INTO EMP VALUES(7788,'SCOTT','ANALYST',7566,'1987-07-03',3000,2000,20);
INSERT INTO EMP VALUES(7839,'KING','PRESIDENT',NULL,'1981-11-17',5000,NULL,10);
INSERT INTO EMP VALUES(7844,'TURNERS','SALESMAN',7698,'1981-09-08',1500,50,30);
INSERT INTO EMP VALUES(7876,'ADAMS','CLERK',7566,'1987-07-13',1100,NULL,20);
INSERT INTO EMP VALUES(7900,'JAMES','CLERK',7698,'1981-12-03',1250,NULL,30);
INSERT INTO EMP VALUES(7902,'FORD','CLERK',7566,'1981-12-03',3000,NULL,20);
INSERT INTO EMP VALUES(7934,'MILLER','CLERK',7782,'1981-01-23',1300,NULL,10);

--  Pay scale 
CREATE TABLE SALGRADE( 
	GRADE INT,--  Grade 
	LOSAL DOUBLE, --  minimum wage 
	HISAL DOUBLE 
); --  Maximum wage 
INSERT INTO SALGRADE VALUES (1,500,1000);
INSERT INTO SALGRADE VALUES (2,1001,1500);
INSERT INTO SALGRADE VALUES (3,1501,2000);
INSERT INTO SALGRADE VALUES (4,2001,3000);
INSERT INTO SALGRADE VALUES (5,3001,9999);

All the query statements practiced

--  Find in Department 30 Employee details 
SELECT*
FROM emp
WHERE DEPTNO=30

--  Find out the number of the employee who works as an employee , full name , Department number 
SELECT EMPNO  Number ,ENAME  full name ,DEPTNO  Department number 
FROM emp
WHERE JOB='CLERK'

--  Retrieve the information of employees whose bonus is more than the basic wage 
SELECT*
FROM emp
WHERE	COMM>SAL

--  Search bonus is more than% of basic salary 60 Employee information 
SELECT *
FROM emp
WHERE COMM>SAL*0.6;

--  Find out if the name contains A Employee information 
-- % wildcard , Express 0~n Any character 
SELECT *
FROM emp
WHERE ENAME like '%A%';

--  Find out the name to a,b,s Employee information at the beginning 
--  wildcard ^ Means to calculate from the beginning 
-- [] The wildcard character indicates that [] Any character in 
SELECT*
FROM emp
WHERE ENAME REGEXP '^[abs]';

--  Find the name with length 7 Employee information in characters 
-- LENGTH（str） Function to get the length of the string 
SELECT *
FROM emp
WHERE LENGTH(ENAME)=7;

--  The name does not contain R Character employee information 
SELECT*
FROM emp
WHERE ENAME NOT LIKE '%R%';

--  Return employee details and sort them in ascending order by name 
--  keyword ORDER BY, among ASC Ascending ,DESC Descending 
SELECT *
FROM emp
ORDER BY ENAME ASC;

--  Return employee information in descending order by name , Wages are in ascending order 
--  The sort constraints used first are placed first 
SELECT *
FROM emp
ORDER BY ENAME DESC,SAL+COMM ASC;

--  Calculate the employee's daily salary ( Press 30 God )
SELECT SAL/30  per diem 
FROM emp;

--  Find out the jobs of the employees who get the bonus 
SELECT JOB
FROM emp
WHERE COMM IS NOT NULL
GROUP BY JOB;

--  Find out if the bonus is less than 100 Or information about employees who don't get bonuses .
-- NULL Unavailable < Judge , application IS NULL
SELECT *
FROM emp
WHERE COMM<100 or COMM is NULL;

--  find 10 The manager of the Department 、20 The staff of the Department   Employee information .
SELECT*
FROM emp
WHERE DEPTNO=10 AND JOB='MANAGER' OR DEPTNO=20 AND JOB='CLERK';

--  find 10 The manager of the Department 、20 The staff of the Department   Or it's not a manager or an employee, but the salary is higher than 2000 Employee information for .
SELECT*
FROM emp
WHERE DEPTNO=10 AND JOB='MANAGER' OR DEPTNO=20 AND JOB='CLERK' OR SAL>2000;

--  Return the department number and the minimum wage of the Department .
SELECT DEPTNO as  department ,MIN(SAL) as  minimum wage 
FROM emp
GROUP BY DEPTNO;

--  Check the employee's name and annual salary , And sort by annual salary in descending order 
SELECT ENAME  Employee name ,MGR  Annual salary 
FROM emp
ORDER BY MGR DESC

--  Return to the employee's job and the minimum wage for the job .
SELECT MIN(SAL)  minimum wage ,JOB
FROM emp
GROUP BY JOB;

--  Find and SCOTT Information about employees engaged in the same work 
SELECT*
FROM emp
WHERE JOB=(
	SELECT JOB
	FROM emp
	WHERE ENAME='SCOTT'
);

--  Pay more than JAMES Employee information 
SELECT *
FROM emp
WHERE SAL>(
	SELECT SAL
	FROM emp
	WHERE ENAME='JAMES'
);

--  Return the employee information whose salary is greater than the average salary 
SELECT*
FROM emp
WHERE SAL>(
	SELECT AVG(SAL)
	FROM emp
);

--  Return the names of all employees in the sales department 
SELECT ENAME
FROM emp
WHERE DEPTNO=(
	SELECT DEPTNO
	FROM dept
	WHERE DNAME='SALES'
);

--  Return pay is higher than 30 Information about all employees in the Department .
SELECT*
FROM emp
WHERE SAL>(
	SELECT AVG(SAL)
	FROM emp
	WHERE DEPTNO=30
);

--  Return the name of the Department that owns the employee 、 Department number .
--  Display inner connection 
SELECT dept.DNAME  Department name ,emp.DEPTNO
FROM emp
INNER JOIN dept on emp.DEPTNO=dept.DEPTNO;

--  Implicit inner join 
SELECT dept.DNAME,emp.DEPTNO
FROM emp,dept
WHERE emp.DEPTNO=dept.DEPTNO;

--  Return the name of the employee , Department and department name 
SELECT emp.ENAME,dept.DEPTNO,dept.DNAME
FROM emp,dept
WHERE emp.DEPTNO=dept.DEPTNO;

--  Return the name of the employee and the Department 
SELECT ENAME,dept.DNAME
FROM emp,dept
WHERE emp.DEPTNO=dept.DEPTNO and emp.JOB='CLERK'

--  Return department number , Department name , The location of the Department and the total number of employees in each department 
SELECT d1.DEPTNO,d1.DNAME,d1.LOC,e. Total number of employees in the Department 
FROM dept d1,(
	SELECT DEPTNO,count(*)  Total number of employees in the Department 
	FROM emp
	GROUP BY DEPTNO
)e
WHERE d1.DEPTNO=e.DEPTNO; 

--  Return the names of the employee or salesperson and the manager 
SELECT e1.ENAME  staff ,e2.` The manager `  My manager 
FROM emp e1,(
	SELECT DEPTNO,ENAME  The manager 
	FROM emp
	WHERE JOB='MANAGER'
)e2
WHERE e1.DEPTNO=e2.DEPTNO AND e1.JOB!='MANAGER';

--  Return the names of employees and managers whose entry date is earlier than their manager's entry date 
SELECT e1.ENAME  staff ,e2.ENAME  The manager 
FROM emp e1,emp e2
WHERE e1.DEPTNO=e2.DEPTNO AND e2.JOB='MANAGER' and e1.HIREDATE<e2.HIREDATE;

--  Return the employee information of the maximum wage and the minimum wage 
SELECT e1.EMPNO,e1.ENAME,e1.JOB,e1.MGR,e1.HIREDATE,e1.SAL,e1.COMM,e1.DEPTNO
FROM emp e1,(
	SELECT MAX(SAL)  Maximum wage ,MIN(SAL)  minimum wage 
	FROM emp
)e2
WHERE e1.SAL=e2.` minimum wage ` OR e1.SAL=e2.` Maximum wage `;

--  Return the name and salary of the employee whose salary is in the fourth level 
SELECT ENAME,SAL
FROM salgrade s1,emp e1
WHERE e1.SAL>s1.LOSAL and e1.SAL<s1.HISAL and s1.GRADE=4;

--  scene ： Query the average salary is higher than 2000 Set to name and average salary 
SELECT JOB  Job title ,AVG(SAL)  Average wage 
FROM emp
GROUP BY  Job title 
HAVING  Average wage >2000

/** from The subsequent sub query is usually a multi row and multi column table   Multi row and multi column subqueries are usually placed in from after where Before   Pseudotables must define aliases , Otherwise, the query cannot be executed   There is usually no need to write having, Because it consumes a lot of memory , Instead, use subqueries ,  take having The following conditions are placed in the from Back   Father inquiry SELECT The following column query actually queries the column alias of the sub query   That is, through FRom The following statement generates a temporary table , Then look up the data in this temporary table  **/
SELECT  Job title , Average wage 
FROM(
	SELECT JOB  Job title ,AVG(SAL)  Average wage 
	FROM emp
	GROUP BY  Job title 
)e
WHERE  Average wage >2000;

--  Find the department number , Department name , Department Address , Number of departments , Department average wage 
SELECT d.DEPTNO  Department number ,d.DNAME  Department name ,d.LOC  Department Address ,e. Number of departments ,e.` Average wage `
FROM dept d,(
	SELECT DEPTNO,count(*)  Number of departments ,AVG(SAL)  Average wage 
	FROM emp
	GROUP BY DEPTNO
)e 
WHERE d.DEPTNO=e.DEPTNO;

--  Check out all who work in the sales department   Employee label , full name , Basic salary , Bonus , Position , Date of entry   Departmental maximum and minimum wages 
SELECT e1.empno,e1.ename,e1.sal,e1.comm,e1.job,e1.HIREDATE,e2.` Departmental minimum wage `,e2.` The highest salary in the Department `
FROM emp e1,(
	SELECT DEPTNO,max(SAL)  The highest salary in the Department ,min(SAL)  Departmental minimum wage 
	FROM emp
	GROUP BY DEPTNO
)e2
WHERE e1.DEPTNO=e2.DEPTNO and e1.DEPTNO=(
	SELECT DEPTNO
	FROM dept
	WHERE dname='SALES'
)