MySQL 8.4 發行說明
如果您不想看到資料表的整個列,只需指定您感興趣的欄位,並用逗號分隔。例如,如果您想知道您的動物何時出生,請選擇 name
和 birth
欄位
mysql> SELECT name, birth FROM pet;
+----------+------------+
| name | birth |
+----------+------------+
| Fluffy | 1993-02-04 |
| Claws | 1994-03-17 |
| Buffy | 1989-05-13 |
| Fang | 1990-08-27 |
| Bowser | 1989-08-31 |
| Chirpy | 1998-09-11 |
| Whistler | 1997-12-09 |
| Slim | 1996-04-29 |
| Puffball | 1999-03-30 |
+----------+------------+
若要找出誰擁有寵物,請使用此查詢
mysql> SELECT owner FROM pet;
+--------+
| owner |
+--------+
| Harold |
| Gwen |
| Harold |
| Benny |
| Diane |
| Gwen |
| Gwen |
| Benny |
| Diane |
+--------+
請注意,查詢僅從每筆記錄擷取 owner
欄位,其中某些欄位會重複出現。若要最小化輸出,請加入關鍵字 DISTINCT
,以僅擷取每個唯一的輸出記錄一次
mysql> SELECT DISTINCT owner FROM pet;
+--------+
| owner |
+--------+
| Benny |
| Diane |
| Gwen |
| Harold |
+--------+
您可以使用 WHERE
子句將列選取與欄位選取結合。例如,若要僅取得狗和貓的出生日期,請使用此查詢
mysql> SELECT name, species, birth FROM pet
WHERE species = 'dog' OR species = 'cat';
+--------+---------+------------+
| name | species | birth |
+--------+---------+------------+
| Fluffy | cat | 1993-02-04 |
| Claws | cat | 1994-03-17 |
| Buffy | dog | 1989-05-13 |
| Fang | dog | 1990-08-27 |
| Bowser | dog | 1989-08-31 |
+--------+---------+------------+