Can I use the result of a select statement from mysql to compare it with a variable?

Question

I have the following code in the my stored procedure:

SET cont_email = SELECT email from contacts  WHERE id=in_id;

IF in_customer_email = cust_email then

**do something**

So, I was wondering if instead of creating a local variable and storing the result from the SELECT statement I just paste it directly in the if statement like so:

IF in_customer_email = (SELECT email from contacts  WHERE id=in_id) then

    **do something**

Also, I was wondering how I can use ORs in MySQL.

Can I do this?

IF in_customer_email = customer_email OR in_customer_name = customer_name THEN

I have seen the use of OR like this:

SELECT customer_id, customer_name
FROM customers
WHERE (customer_name = 'Apple' OR customer_name = 'Samsung')

but never inside of an if statement, so I wasn't sure.

And lastly, it has been ages since I could use something like if var1 = var2 , since this is usually used for assigning not to compare, so I was wondering if this correct or I have to use double equal sign like var1 == var2 .

Thanks.

Answer 1

Variable vs. Nested Statement?

IF in_customer_email = (SELECT email from contacts  WHERE id=in_id) then

**do something**

This is a perfectly legal query -- no need to declare the variable beforehand.

ORs in IF Statements?

IF in_customer_email = customer_email OR in_customer_name = customer_name THEN

This is also perfectly legal (and often quite useful).

Use = or == to Compare Values?

if var1 = var2

This is, contrary to what your programmer spidey-sense may indicate, the proper way to compare values in MySQL queries.