MySQL query

Simple query

It is preferred to create a database and import the required sql file

View table structure

 

Query a field

Check the name of the employee

  

Select The statement is followed by the field name ,select Is the key word ,select And field names are separated by spaces ,from Represents the table to query , It is separated from the field by a space

Query multiple fields

Query employee's number and name

Query multiple fields ,select Fields in adopt comma Interval is enough , The last field , That is to say from The preceding fields cannot use commas  

Query all fields

Conditions of the query

Conditional query needs to use where sentence ,where It must be put in from After the statement table

The following operators are supported

Operator	explain
=	be equal to
<> or !=	It's not equal to
<	Less than
<=	Less than or equal to
>	Greater than
>=	Greater than or equal to
between … and ….	Between two values , Equate to >= and <=
is null	by null（is not null Not empty ）
and	also
or	perhaps
in	contain , It's equivalent to more than one or（not in Not in this range ）
not	not You can take non , Mainly used in is or in in
like	like It is called fuzzy query , Support % Or underline match % Match any character Underline , An underscore matches only one character

  Example

The inquiry salary is 5000 The employees'

  Usage is in where Add the required conditions and operators after

like Can fuzzy query

Check the name with M At the beginning, all the employees