Advanced data filtering (like)

Single character filter ' _ '

SELECT * from T_employee where FName like ' _erry '

Multi-character filter '% '

SELECT * from T_employee where FName like ' t% '

Set match filter [JT]: Information for the first letter J or T

[^JT] Anti-collection: information for the first letter not J or T

SELECT * from T_employee where FName like ' [jt]% '

SELECT * from T_employee where FName like ' [^jt]% '

SQL query null value, can not directly use ordinary equals to judge, to use the keyword ' is null/is not null ', because some special settings in the database will not be queried

SELECT * from T_employee where Fage is null
SELECT * from T_employee where Fage are not null and fsalary>2000

Inverse operator '! = does not equal! < not less than ' three ways of expression '! ' Can only be used in SQL Server DB2 database

SELECT * from T_employee where fage!=23 and fsalary!<5000
SELECT * from T_employee where fage<>23 and fsalary>=5000
SELECT * from T_employee where not (fage=23) and not (fsalary<5000) not inverse operation

Advanced data filtering (like)