Question

If I have a list of ID’s that I have selected from a statement

SELECT id FROM myTable WHERE name = 'TEST'

This would return just the ids (1001, 1002, 1003, etc…) Then I want to perform another SELECT statement to retrieve all the titles for all those ids.

SELECT title FROM myTable2 WHERE id = XXXX

the id in table2 is the foreign key of table2. id in myTable is the Primary Key. How can I go about retrieving all the titles from those ids. I was thinking about storing all the results of the first select statement in an array, and then using a while loop to iterate through the list and return each result into another array, but my fear is that when the database gets big if it has to return 1000 rows that could be some bad overhead. So in PHP or SQL what is the best way to perform this?

Answer 1

You can use a subquery:

SELECT title
FROM myTable2
WHERE id IN (
 SELECT id 
  FROM myTable
  WHERE name = 'TEST'
)

Another way to do it would to be use a JOIN, to avoid the sub-query:

SELECT title
FROM myTable2 
LEFT JOIN myTable
 ON myTable.id = myTable2.id
WHERE myTable.name = 'TEST'