SQL查询从一个表获取所有记录，除特定记录，按日期，从另一个表

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 (ie Table2 date). I apologize, but I do not have a specific piece of code to include since nothing has worked for me.

Answer 1

USE INNER JOIN if you are sure that T1id exists in both tables:

SELECT  a.T1id, 
        a.FirstName, 
        a.LastName, 
        b.hours, 
        b.rate, 
        b.date
FROM table1 a INNER JOIN table2 b
        ON a.T1id = b.T1id
WHERE b.date <> DATE('2012-02-08')

but if you want to get all T1id from Table1 (which exists or does not exists in Table2 ) use LEFT JOIN

SELECT  a.T1id, 
        a.FirstName, 
        a.LastName, 
        b.hours, 
        b.rate, 
        b.date
FROM table1 a LEFT JOIN table2 b
        ON a.T1id = b.T1id
WHERE b.date <> DATE('2012-02-08')

Answer 2

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