根據列值選擇不同的行

Question

在一個表中，我有四列'FirstName'，'LastName'，'Dob'，'Number'唯一的'first Name'和'LastName'有多行，它們可以有相同或不同的'Number'和'Dob' '價值觀

FirstName  LastName   Dob         Number
Alice      Smith      02/03/77    0876543    (require)
Alice      Smith      Null        0876543    (Not require)
Alice      Smith      Null        Null       (Not require)
John       Adam       11/28/63    3265783    (require)
John       Adam       11/28/63    Null       (Not Require)
John       Adam       05/15/58    Null       (require)
Sally      Smith      Null        Null       (require)

我想要不同的行，但是如果'Number'或'Dob'與其他FirstName'和'LastName'的記錄匹配，我只需要一條記錄我在上面的示例中查找標記為'require'的行。 我試過的組合沒有得到我認為會有的結果。 謝謝

Answer 1

我首先選擇填充了所有四個字段的所有行：

SELECT DISTINCT FirstName, LastName, Dob, Number
FROM customers
WHERE Dob IS NOT NULL And Number IS NOT NULL

然后我會在選擇中添加第一個選擇中不存在的NOT NULL值的記錄：

with RequiredSet as (
SELECT DISTINCT FirstName, LastName, Dob, Number
FROM customers
WHERE Dob IS NOT NULL And Number IS NOT NULL
), AdditionalSet as (
SELECT distinct c.FirstName, c.LastName, c.Dob, c.Number
FROM customers c
WHERE Dob IS NOT NULL And NOT EXISTS(SELECT 1 
   FROM RequiredSet r 
   WHERE r.FirstName = c.FirstName And r.LastName=c.LastName And r.Dob=c.Dob)
OR Number IS NOT NULL And NOT EXISTS(SELECT 1 
   FROM RequiredSet r 
   WHERE r.FirstName = c.FirstName And r.LastName=c.LastName And r.Number=c.Number)
)
SELECT FirstName, LastName, Dob, Number
FROM RequiredSet
UNION ALL 
SELECT FirstName, LastName, Dob, Number
FROM AdditionalSet