MINUS operator in MySQL query [duplicate] - mysql

Question

I am trying to perform a MINUS operation in MySql.I have three tables:
one with service details
one table with states that a service is offered in
another table (based on zipcode and state) shows where this service is not offered.
I am able to get the output for those two select queries separately. But I need a combined statement that gives the output as
'SELECT query_1 - SELECT query_2'.
Service_Details Table
Service_Code(PK) Service Name
Servicing_States Table
Service_Code(FK) State Country PK(Service_Code,State,Country)
Exception Table
Service_Code(FK) Zipcode State PK(Service_Code,Zipcode,State)

Answer 1

MySql does not recognise MINUS and INTERSECT, these are Oracle based operations. In MySql a user can use NOT IN as MINUS (other solutions are also there, but I liked it lot).
Example:
select a.id
from table1 as a
where <condition>
AND a.id NOT IN (select b.id
from table2 as b
where <condition>);

Answer 2

MySQL Does not supports MINUS or EXCEPT,You can use NOT EXISTS, NULL or NOT IN.

Answer 3

Here's my two cents... a complex query just made it work, originally expressed with Minus and translated for MySql
With MINUS:
select distinct oi.`productOfferingId`,f.name
from t_m_prod_action_oitem_fld f
join t_m_prod_action_oitem oi
on f.fld2prod_action_oitem = oi.oid;
minus
select
distinct r.name,f.name
from t_m_prod_action_oitem_fld f
join t_m_prod_action_oitem oi
on f.fld2prod_action_oitem = oi.oid
join t_m_rfs r
on r.name = oi.productOfferingId
join t_m_attr a
on a.attr2rfs = r.oid and f.name = a.name;
With NOT EXISTS
select distinct oi.`productOfferingId`,f.name
from t_m_prod_action_oitem_fld f
join t_m_prod_action_oitem oi
on f.fld2prod_action_oitem = oi.oid
where not exists (
select
r.name,f.name
from t_m_rfs r
join t_m_attr a
on a.attr2rfs = r.oid
where r.name = oi.productOfferingId and f.name = a.name

Answer 4

The tables have to have the same columns, but I think you can achieve what you are looking for with EXCEPT... except that EXCEPT only works in standard SQL! Here's how to do it in MySQL:
SELECT * FROM Servicing_states ss WHERE NOT EXISTS
( SELECT * FROM Exception e WHERE ss.Service_Code = e.Service_Code);
http://explainextended.com/2009/09/18/not-in-vs-not-exists-vs-left-join-is-null-mysql/
Standard SQL
SELECT * FROM Servicing_States
EXCEPT
SELECT * FROM Exception;

Answer 5

An anti-join pattern is the approach I typically use. That's an outer join, to return all rows from query_1, along with matching rows from query_2, and then filtering out all the rows that had a match... leaving only rows from query_1 that didn't have a match. For example:
SELECT q1.*
FROM ( query_1 ) q1
LEFT
JOIN ( query_2 ) q2
ON q2.id = q1.id
WHERE q2.id IS NULL
To emulate the MINUS set operator, we'd need the join predicate to compare all columns returned by q1 and q2, also matching NULL values.
ON q1.col1 <=> q2.col2
AND q1.col2 <=> q2.col2
AND q1.col3 <=> q2.col3
AND ...
Also, To fully emulate the MINUS operation, we'd also need to remove duplicate rows returned by q1. Adding the DISTINCT keyword would be sufficient to do that.

Answer 6

In case the tables are huge and are similar, one option is to save the PK to new tables. Then compare based only on the PK. In case you know that the first half is identical or so add a where clause to check only after a specific value or date .
create table _temp_old ( id int NOT NULL PRIMARY KEY )
create table _temp_new ( id int NOT NULL PRIMARY KEY )
### will take some time
insert into _temp_old ( id )
select id from _real_table_old
### will take some time
insert into _temp_new ( id )
select id from _real_table_new
### this version should be much faster
select id from _temp_old to where not exists ( select id from _temp_new tn where to.id = tn.id)
### this should be much slower
select id from _real_table_old rto where not exists ( select id from _real_table_new rtn where rto.id = rtn.id )