How to LEFT JOIN two tables with the same column name

Question

I want to LEFT JOIN two tables with the same column name. I have two tables which I am trying to join but I keep getting an error:

column 'id' is ambiguous

returned in my JSON output.

My current query:

$sQuery = "
 SELECT SQL_CALC_FOUND_ROWS ".str_replace(" , ", " ", implode(", ", $aColumns))."
 FROM   $sTable
 LEFT JOIN
    $sTable2
    ON ($sTable2.id = $sTable.id)

 $sWhere
 $sOrder
 $sLimit
";

Produces that error. How can I join these two tables as the join point when there is the same column name in each table?

Answer 1

Be explicit about which table the column belongs to. This also applies to the SELECT part of the query:

SELECT table1.column AS column1, table2.column AS column2
FROM table1
LEFT JOIN table2
ON table1.column = table2.column

To save you some typing time, use table aliases:

SELECT t1.column AS column1, t2.column AS column2
FROM table1 AS t1
LEFT JOIN table2 AS t2
ON t1.column = t2.column

Answer 2

The ambiguity is probably in the select, not in the join. The join looks OK. $aColumns probably contains "id" without table name specification or something.

Answer 3

The LEFT JOIN keyword returns all rows from the left table (table_name1), 
even if there are no matches in the right table (table_name2).

In your case, both table1 and table 2 are same. So There might be no benefit of doing Left Join because ultimately all the rows will be returned. You might wanna use Inner Join.