使用MIN（）进行左联接而没有重复值

“通用” SQL方式：

SELECt table_1.custno,table_2.qty,table_2.descr FROM table_1, table_2 WHERe table_2.id = (SELECt TOP 1 id          FROM table_2          WHERe custno = table_1.custno          ORDER BY qty )

SQL 2008方式（可能更快）：

SELECt custno, qty, descr FROM(SELECt     custno,     qty,     descr,    ROW_NUMBER() OVER (PARTITION BY custno ORDER BY qty) RowNum    FROM table_2) AWHERe RowNum = 1