在另一个查询中使用查询结果

Question

我有一个问题：

$sql1="SELECT column1 FROM table_A WHERE username LIKE '".$username."';"; 
// This may return multiple rows

现在，我需要在另一个中使用此查询的结果：

$sql2="select all from table_B where mycolumn equals to result we got above"

Answer 1

试试这个：

$sql = "select all from table_B where mycolumn in (SELECT column1 FROM table_A WHERE username LIKE'".$username."')";

Answer 2

使用JOINS：

 $sql = "SELECT 
                table_B.* 
         FROM table_A 
         INNER JOIN table_B ON (table_A.column1 = table_B.mycolumn)
         WHERE table_A.username LIKE '".$username."'";