--timestamp转换为date(ts字段为timestamp类型)SELECT cast(ts AS DATE) from tab1 WHERE tid=1;--timestamp转换为date(ts字段为timestamp类型)SELECT cast(ts AS DATE) from tab1 WHERE tid=3;--date相减SELECT (SELECT cast(ts AS DATE) from tab1 WHERE tid=3)-(SELECT cast(ts AS DATE) from tab1 WHERE tid=1) FROM dual;--把date转换为妙SELECT ((SELECT cast(ts AS DATE) from tab1 WHERE tid=3)-(SELECT cast(ts AS DATE) from tab1 WHERE tid=1))*24*60*60 FROM dual;