select * from students where age >= 18 and gender = 'F' 
VS 
select * from students where age >= 18 or gender = 'F'

select * from trx_rcd where trx_date < '2020-01-28' or trx_date > '2020-01-28' 
VS 
select * from trx_rcd where trx_date not between '2020-01-28' and '2020-01-28'

select * from students where name in ('Jack', 'Linda') 
VS 
select * from students where name = 'Linda' or 'Jack'

select * from trx_rcd where trx_amt >= 100 and trx_amt < 1000 
VS 
select * from trx_rcd where trx_amt between 100 and 1000

SELECT SUBSTR(email, LOCATE('@', email)) AS domain FROM employees;

SELECT RIGHT(email, LENGTH(email) - LOCATE('@', email)) AS domain FROM employees;

SELECT SUBSTRING_INDEX(email, '@', -1) AS domain FROM employees;

SELECT SUBSTRING_INDEX(email, '@', 1) AS domain FROM employees;

select控制列，where控制列

select控制行，where控制行

select控制列，where控制行

select控制行，where控制列

HAVING

NOT

AND

OR

OR

IN

NOT

AND

gender =' F' OR parent_bg = '公务员' AND total_score > 650 OR (chinese+math+english) > 300

(gender =' F' AND parent_bg = '公务员' AND total_score > 650 ) OR (chinese+math+english) > 300)

(gender =' F' ) AND (parent_bg = '公务员') AND (total_score > 650 OR (chinese+math+english) > 300)

gender =' F' AND parent_bg = '公务员' AND total_score > 650 OR (chinese+math+english) > 300