如何最小化sql select查询的执行时间

Question

I have two tables tbl_order and tbl_order user . i need to select all columns from two tables and match it with order id and status of that corresponding tables

i have use below query

select o.*
     , u.*
     , o.id as ord_id 
  from tbl_order o
     , tbl_order_user u 
 where (o.online='0' or o.online='2') 
   and o.status='0' 
   and o.id = u.oid

My doubt is this query takes max execution time .

How to reduce this max execution time , is there any alternate query for reducing max execution time .

Can anyone help me . Thanks in advance

Answer 1

Use join statements and make sure that you have index on any column you use in WHERE statements and JOIN conditions, with the little info you provided for your schema here is an SQL statement with JOIN:

SELECT o.*, 
       u.*, 
       o.id AS ord_id 
FROM   tbl_order o 
       JOIN tbl_order_user u 
    ON o.id = u.oid 
         AND o.online  IN ('0' ,'2' ) AND o.status = '0'

RDBMS nowadays optimize your SQL query to be as fast as possible, but if you didn't help it it will not be fast, and as mentioned in the comment retrieve only the fields you need in your app for this query,

Note : that you are using string comparison for status and online fields.