使用DISTINCT或EXISTS关键字来排除重复行。
示例:
SELECT DISTINCT table1.column1, table1.column2, table2.column1
FROM table1
LEFT JOIN table2 ON table1.column1 = table2.column1
或者:
SELECT table1.column1, table1.column2, table2.column1
FROM table1
WHERE EXISTS (
SELECT 1
FROM table2
WHERE table1.column1 = table2.column1
)