--Select query criteria query

# Condition Query
 / * 
SELECT 
  query list 
from 
  table 
where filters; 

sequence: from table name -> Filter -> SELECT field 
* / 
# conditional operator 
#   >   <   =   =!   ( <> )   > =   <= 
# Logic operation symbol 
# &&  ||  ^   ( the AND , OR , the nOT ) 
# fuzzy query 
# the LIKE          % , _, Escape 
# bewteen the AND   inclusive, the sequence can not be reversed 
# the IN            value must be the exact value (not write wildcards) 
# the iS  NULL      Equal number can not determine the value NULL 
# IS  the NOT  NULL   does not equal NULL value can not be determined 
# security equal (equal sign) <=> either determine value, but also to determine NULL
 the USE `myemployees`; 

# query wages higher than 12,000. 
The SELECT  
  *  
the FROM 
  `employees` 
the WHERE salary >  12000 ; 

employee # inquiry number is not 90 department name and department number of employees 
the SELECT  
  ` last_name`, 
  `department_id` 
the FROM 
  ` employees` 
the WHERE `department_id` <>  90 ; 

# query to pay 10,000 staff were between 20,000 salary and bonuses 
the SELECT  
  `last_name`, 
  ` salary`, 
  `commission_pct` 
the FROM
  employees` ` 
the WHERE ` salary` >  10000  
  the AND `salary` <  20000 ; 
  
# query sector number is less than 90 or greater than 110, greater than or employee payroll information 15000 
the SELECT  
  *  
the FROM 
  ` employees` 
the WHERE `department_id` <  90  
  OR ` department_id` >  110  
  OR `salary` >  15000 ; 

the SELECT  
  *  
the FROM 
  ` employees` 
the WHERE  the NOT ( 
    `department_id` > =  90  
    the AND ` department_id` <=  110 
  ) 
  ORsalary` ` >  of 15,000 ; 

# query employee information employee name contains the letter a 
# LIKE in % is 0 - the n-number of any characters, _ is an arbitrary character, you can use the \ escape character, you can also specify the character transfer 

the SELECT  
  *  
the FROM 
  `employees` 
the WHERE ` last_name` the LIKE  ' % a% ' ; 

# inquiry staff were second character is _ employee information 
#ESCAPE the escape character is defined as the $ 
the SELECT  
  *  
the FROM 
  `employees` 
the WHERE ` last_name` the LIKE  ' _ % _ $ '  the ESCAPE  ' $ ' ;