[Interview Abuse] - Common SQL Statements

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create table

create table emp(

id decimal,

name char(10),

age decimal)

 

delete table

DROP TABLE EMP

 

Insert default value

CREATE TABLE EMP(

　　Id decimal NOT NULL,

　　Name char(10) NOT NULL,

　　Age decimal NOT NULL DEFAULT 18)

 

add column

ALTER TABLE EMP ADD COLUMN Comments char(50) NOT NULL DEFAULT 'COMMENTS'

 

delete column

ALTER TABLE EMP DROP COLUMN Comments

 

Modify column

ALTER TABLE EMP MODIFY COLUMN Comments char(30)

 

create index

CREATE INDEX Name_index ON EMP (Name)

 

Query data

SELECT Name FROM EMP

 

Query unique data

SELECT DISTINCT Name FROM EMP

 

Sort query results

SELECT Name FROM EMP ORDER BY Name

 

Conditional query

SELECT Name FROM EMP WHERE Age < 20

SELECT Name FROM EMP WHERE Age BETWEEN 20 AND 30

 

insert data

INSERT INTO EMP VALUES(123,'xingoo',18)

 

change the data

UPDATE EMP SET Name='xingoo1111' WHERE Name='xingoo'

 

delete data

DELETE FROM EMP WHERE Age<20

 

average

SELECT AVG(Age) FROM EMP

 

Number of queries

SELECT COUNT(DISTINCT Name) FROM EMP

SELECT COUNT(*) FROM EMP

 

Reprinted in: https://my.oschina.net/u/204616/blog/545504