Tuesday, September 1, 2009
How to compare data in two Tables in MySQL?
Problem/Query:
How to compare data in two tables in MySQL?
Example:
| Table A | Table B |
Customers
|
Customers_Backup
|
You may want to check if "Table A" matches all the content of "Table B". If the result is positive then go on and if the result is negative for some rows then print a log
Solution:
select (case when exists (select username from table1 where username not in (select username from table2) ) then 'Active' else 'Inactive' end as result;
Using Case Statement in Table Columns:
select (case userstatus when 'Y' then 'Active' else 'Inactive' end) as status from users;
Note:
Reference:
http://dev.mysql.com/doc/refman/5.0/en/exists-and-not-exists-subqueries.html
http://dev.mysql.com/doc/refman/5.0/en/case-statement.html
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