Conditional query-fuzzy query

Fuzzy query (all for string operations)

Fuzzy query is a bit similar to regular expressions, but it is not as powerful as regular expressions.

Wildcard characters: _,%, [], ^   

    _ Represents any single string.

select * from Student_Info where Name like '张_'

In this way, find the name of Zhang in the Name column of the Student_Info table, two words; it will not find out the name of Zhang.

Another way is

select * from Student_Info where Name like '张%' and len(Name)=2

How to find Zhang XX, three words

select * from Student_Info where Name like '张__'

% Matches any number of any characters

As long as the first word in the query name is Zhang. No matter how many characters there are.

select * from Student_Info where Name like '张%'

 

[] Indicates the scope of filtering.

The middle of the query surname Zhang is a number and the third is a Chinese character.

select * from Student_Info where Name like '张[0-9]三'

The middle of the query surname Zhang is a number or letter, and the third is a Chinese character.

select * from Student_Info where Name like '张[0-9][a-z]三'

 

^ Means not

Query Zhang Mousan, that is, there cannot be a number in the middle.

select * from Student_Info where Name like '张[0-9]三'

 

 

Expand and replace the REPLACE keyword

update Student_Info set Name=replace(Name,'张'，'李')

In this way, all those with the surname Zhang are replaced by those with the surname Li.