Database foundation: select basic query statement

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data The basic query statement specification of the library is ：select Area from Table name

Query the specified table

select * from Table name

*： Represents all columns

Example ：select * from TL_REQUEST

Query specified column

select Name from Table name

Name ： Represents to search from the specified column name

,： If it is to find the corresponding multiple columns , Then use English commas to separate

Example ： select BU_NO from TL_REQUEST select BU_NO,BU_NM from TL_REQUEST

Conditions of the query

select * from Table name where Conditions

*： Represents all columns

Conditions ： It's usually where Conditional expression

The query column contains numbers or letters ：select * from Table name where Name =’ value ’

Example ： select * from TL_REQUEST where BU_NO=’1234′ select * from TL_REQUEST where BU_NM=’ Xiaofang ’

Range queries

select * from Table name where Name between ‘A’ and ‘B’

or

select * from Table name where Name >=’A’ and Name <=’B’

Example ： select*from TL_REQUEST where BU_NO between ‘1000’ and ‘1234’ select*from TL_REQUEST where BU_NO>=’1000′ and BU_NO<=’1234′

Multiconditional query

Or conditional query ：or

select * from Table name where Name =’A’ or Name =’B’

Example ：select * from TL_REQUEST where BU_NO=’1000′ or BU_NO=’1234′

And condition query ：and

select * from Table name where Name =’A’and Name =’B’

Example ：select * from TL_REQUEST where BU_NO=’1000′ and CONTRACT_NO=’tl001′

Discrete queries

Include value query ：in()

select * from Table name where Name =’A’ Name =’B’ Name =’C’

or ：

select * from Table name where Name in(‘A’,’B’,’C’)

Example ： select * from TL_REQUEST where BU_NO=’1000′ BU_NO=’1234′ BU_NO=’1311′ or ： select * from TL_REQUEST where BU_NO in(‘1000′,’1234′,’1311’)

Query without value ：not in()

select * from Table name where Name not in(‘A’,’B’,’C’)

Example ：select * from TL_REQUEST where BU_NO not in(‘1000′,’1234′,’1311’)

Fuzzy query

The query column contains specific Chinese ：select * from Table name where Name like ‘% chinese %’

Like： Add... Before the name .

%： Any number of characters .

_： The underscore indicates any character .

Example ：select * from TL_REQUEST where BU_NM like ‘% ladyfy %’ Or query the situation where the second character is Fang select * from TL_REQUEST where BU_NM like ‘%_ Fragrant %’

Go to check again

select distinct Name from Table name

Example ：select distinct BU_NO from TL_REQUEST

Combination query

select distinct Name from Table name where Conditions

Example ：select distinct BU_NO from TL_REQUEST where BU_NO between ‘1000’ and ‘1234’

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