在多列上使用 DISTINCT 的 SQL SELECT

Question

在 SQL 中，也可以使用 DISTINCT 子句添加多個字段。 DISTINCT 將消除所有選定字段都相同的行。

SQL 代碼：

SELECT agent_code, ord_amount, cust_code, ord_num
FROM orders 
WHERE agent_code='A002';

ORD_NUM ORD_AMOUNT ADVANCE_AMOUNT ORD_DATE CUST_CODE AGENT_CODE

---

200114       3500           2000 15-AUG-08 C00002          A008
200122       2500            400 16-SEP-08 C00003          A004
200118        500            100 20-JUL-08 C00023          A006
200119       4000            700 16-SEP-08 C00007          A010
200121       1500            600 23-SEP-08 C00008          A004
200130       2500            400 30-JUL-08 C00025          A011
200134       4200           1800 25-SEP-08 C00004          A005
200108       4000            600 15-FEB-08 C00008          A004
200103       1500            700 15-MAY-08 C00021          A005
200105       2500            500 18-JUL-08 C00025          A011
200109       3500            800 30-JUL-08 C00011          A010
200101       3000           1000 15-JUL-08 C00001          A008
200111       1000            300 10-JUL-08 C00020          A008
200104       1500            500 13-MAR-08 C00006          A004
200106       2500            700 20-APR-08 C00005          A002
200125       2000            600 10-OCT-08 C00018          A005
200117        800            200 20-OCT-08 C00014          A001
200123        500            100 16-SEP-08 C00022          A002
200120        500            100 20-JUL-08 C00009          A002
200116        500            100 13-JUL-08 C00010          A009
200124        500            100 20-JUN-08 C00017          A007
200126        500            100 24-JUN-08 C00022          A002
200129       2500            500 20-JUL-08 C00024          A006
200127       2500            400 20-JUL-08 C00015          A003
200128       3500           1500 20-JUL-08 C00009          A002
200135       2000            800 16-SEP-08 C00007          A010
200131        900            150 26-AUG-08 C00012          A012
200133       1200            400 29-JUN-08 C00009          A002
200100       1000            600 08-JAN-08 C00015          A003
200110       3000            500 15-APR-08 C00019          A010
200107       4500            900 30-AUG-08 C00007          A010
200112       2000            400 30-MAY-08 C00016          A007
200113       4000            600 10-JUN-08 C00022          A002
200102       2000            300 25-MAY-08 C00012          A012

輸出：

AGENT_CODE ORD_AMOUNT CUST_CODE     ORD_NUM
---------- ---------- ---------- ----------
A002             2500 C00005         200106
A002              500 C00022         200123
A002              500 C00009         200120
A002              500 C00022         200126
A002             3500 C00009         200128
A002             1200 C00009         200133
A002             4000 C00022         200113

想要優化我的查詢

Answer 1

您似乎希望保留最早出現的每個不同名稱。 一種選擇使用子查詢：

SELECT ID, Name, Date
FROM yourTable t1
WHERE Date = (SELECT MIN(Date) FROM yourTable t2 WHERE t2.Name = t1.Name)

請注意，如果兩條具有最短日期的記錄並列，則此解決方案將返回每個名稱組的多個記錄。 但樣本數據似乎並不暗示會發生這種情況。

Answer 2

這是你想要的嗎？

select min(id),name, min(date) from table_1  group by name

Answer 3

看起來您正在尋找每個名稱的最早日期。 這個查詢將實現這一點。 它將按名稱對其進行分組並給出該名稱的最短日期。

SELECT Name,MIN(Date) FROM table_1 GROUP BY Name