SQL basic grammar record

Basic syntax of SQL

1:select sno,sname from student where sage between 20 and 30-find out people between 20 and 30 years old

2:select sno,sname from student where sage is null-query empty age persons from the student table

3:select sno,sname from student where sname= "cary" or sname= "mina" or sname "amy"-query the student number and name of cary,mina,amy

You can also use select sno,sname from student where sname in ('cary','mina','amy') to achieve the same function

Select part

1:AS can rename fields

2:distinct deduplicates values

3: aggregate function () avg (), max (), min (), sum (), count ()

4:TOP 5 first 5 rows of data select top 5 sno,sname from student

The 5:Into select top 5 into testtable from student stores the queried TOP 5 data in the testtable table, which exists in the

In the table in the master database

Select sno,sname,sage,sex into test table02 from student where 11-get student table structure

From part

1: table rename

Select bookname from book as T1 as T2 where t1.id=t2.id-rename T1 borrowbook to T2 for the book table

2: combine subquery

Select distinct bookname from book as T1, (select distinct bookid from borrowbook) as T2 where t1.bookid=t2.bookid

Where part

1: number: =, >, =