Common SQL statements

Commonly used SQL sentence ：

1、 Create database

CREATE DATABASE database-name;

3、 Delete database

DROP DATABASE database-name;

5、 Create new table

create table depart (dept_id int(11) NOT NULL AUTO_INCREMENT, 
dept_name varchar(255) DEFAULT NULL, PRIMARY KEY (dept_id)); 

8、 Create a new table from an existing table ：

create table tab_new like tab_old ( Use old table B Create new table A) 

10、 remarks ： In this way, the table B Copied to the A When will the watch B Copy the complete field structure and index to the table A In the to

create table tab_new as select col1,col2… from tab_old definition only 

12、 remarks ： In this way, only the table B The field structure of is copied to the table A In the to , But the table will not be copied B Index to table in A In the to . This method is flexible. You can specify which fields to copy while copying the original table structure , You can also add field structure to the self copying table as needed .
create table as select A complete copy of the data in the original table , But the indexes in the table structure will be lost .
create table like Only the table creation statement of the original table will be copied completely , But the data will not be copied .
15、 Delete new table

drop table tabname;

17、 Add a column

alter table tabname add column column_name type

19、 Add primary key ： Alter table tabname add primary key(col) 
20、 Delete primary key ： Alter table tabname drop primary key 
21、 A data table can only have one primary key , Therefore, there is no primary key to delete a column .
22、 Create index ：create [unique] index idxname on tabname(col….) 
23、 Delete index ：drop index idxname 
24、 notes ： The index is immutable , If you want to change it, you must delete and rebuild .
25、 Create view ：create view viewname as select statement 
26、 Delete view ：drop view viewname
27、 A few simple basic sql sentence  
28、 choice ：select * from table1 where  Range  
29、 Insert ：insert into table1(field1,field2) values(value1,value2) 
30、 Delete ：delete from table1 where  Range  
31、 to update ：update table1 set field1=value1 where  Range  
32、 lookup ：select * from table1 where field1 like ’%value1%’ 
33、 Sort ：select * from table1 order by field1,field2 [desc] 
34、desc： Descending ,asc： Ascending  
35、 total ：select count as totalcount from table1 
36、 Sum up ：select sum(field1) as sumvalue from table1 
37、 Average ：select avg(field1) as avgvalue from table1 
38、 Maximum ：select max(field1) as maxvalue from table1 
39、 Minimum ：select min(field1) as minvalue from table1
40、 grouping :Group by: 

41、 A watch , Once the grouping is complete , Only group related information can be obtained after query . 
42、 Group related information ：（ Statistics ） count,sum,max,min,avg 
43、 Copy table select * into b from a where 1<>1
44、 Subquery ( Table name 1：a  Table name 2：b) select a,b,c from a where a IN (select d from b ) 
45、 Show article 、 The author and the final response time  
46、select a.title,a.username,b.adddate from table a,(select max(adddate) adddate from table where table.title=a.title) b
47、 View query ( Table name 1：a ) 
48、select * from (SELECT a,b,c FROM a) T where t.a > 1;
49、between Usage of ,between The boundary value is included when the query data range is limited ,not between barring  
50、select * from table1 where time between time1 and time2 
51、select a,b,c, from table1 where a not between  The number 1 and  The number 2
52、in  How to use  
53、select * from table1 where a [not] in (‘ value 1’,’ value 2’,’ value 4’,’ value 6’)
54、 Two related tables , Delete the information in the primary table that is not in the secondary table  
55、delete from table1 where not exists ( select * from table2 where table1.field1=table2.field1 )
56、 Schedule five minutes in advance to remind  
57、SQL: select * from  Schedule  where datediff(‘minute’,f Starting time ,getdate())>5
58、 front 10 Bar record  
59、select top 10 * form table1 where  Range 
60、 Choose in each group b The data with the same value corresponds to a The biggest record of all information ( Similar usage can be used for forum monthly leaderboards , Monthly hot product analysis , Rank by subject score , wait .) 
61、select a,b,c from tablename ta where a=(select max(a) from tablename tb where tb.b=ta.b)
62、 Including all in  TableA  But not in  TableB and TableC  The result table is derived by eliminating all duplicate rows  
63、(select a from tableA ) except (select a from tableB) except (select a from tableC)
64、 Random take out 10 Data   select top 10 * from tablename order by newid()