Question

I am trying to SELECT records from two MySql tables. I would like all records from the first table excluding specific records, by date, from the second table. For example:

Table1 T1id, firstName, LastName
Table2 id, T1id, hours, rate, date

T1id is the link between the two tables, therefore when the tables are joined I would have T1id, firstName, lastName, hours, rate, date

Let’s say there is a record in Table2 with a date of 2012-02-08. With one query, I need to select all records from Table1, excluding the record from Table2 that has the date of 2012-02-08.

I’ve tried a few variations of JOINS and UNIONS, however I either get all records, a bunch of duplicate records, or one record (i.e. Table2 date). I apologize, but I do not have a specific piece of code to include since nothing has worked for me.

Answer 1

So many times this is typically done with a NOT EXISTS subquery, but subqueries can be big performance hits in larger tables… However, by doing a LEFT JOIN and looking for NULL is in essence, the same result

select
      t1.*
   from
      table1 t1
         left join table2 t2
            on t1.t2.t1id
          AND t2.date = '2012-02-08'
   where
      t2.t1id IS NULL