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[英]SQL Server : read nested JSON from a table and find the MAX value
[英]SQL:Finding max value from a nested JSON in SQL Server
這個問題在這個 SO 線程中有一個參考。
我想計算下面 JSON 的MAX()
值。 此外,其中的鍵也不是固定的,因此根據上述解決方案,它們不能在代碼中硬編碼。
DECLARE @json nvarchar(max) = ''{"value": [
{
"AEDAT": "20211119",
"ERDAT": "20211119"
},
{
"AEDAT": "20211119",
"ERDAT": "20211112"
},
{
"AEDAT": "20211123",
"ERDAT": "20211123"
},
{
"AEDAT": "00000000",
"ERDAT": "20211119"
},
{
"AEDAT": "00000000",
"ERDAT": "20211123"
}]}';
此外,我將從其他一些 SP 獲取以下字符串作為參數。
DECLARE @ColumnName = 'AEDAT,ERDAT' ---I shall be getting this as an output from another SP.
綜上所述,我的做法如下:
DECLARE @col_table TABLE (ID int IDENTITY(1,1), ColumnName varchar(100))
INSERT INTO @col_table SELECT value as ColumnName FROM STRING_SPLIT(@ColumnName,',');
DECLARE @max_val TABLE (ID int IDENTITY(1,1), LastUpdatedValue int)
DECLARE @max_ID int
DECLARE @min_ID int
DECLARE @1st_col varchar(max)
SELECT @max_ID = MAX(ID),@min_ID = MIN(ID) FROM @col_table GROUP BY ColumnName;
WHILE (@min_ID <= @max_ID)
BEGIN
SELECT @1st_col = ColumnName FROM @col_table WHERE ID = @min_ID
INSERT INTO @max_val (LastUpdatedValue)
SELECT JSON_VALUE(j.value,'$.' +@1st_col+ '' ) FROM OPENJSON(@json,'$.value') AS j
SET @min_ID = @min_ID + 1
END
理想情況下,上述方法應該給出 10 個值(AEDAT 和 ERDAT 各 5 個)但這給了我 5 個值。
SELECT * FORM @max_val;
ID LastUpdatedValue
1 20211119
2 20211112
3 20211123
4 20211119
5 20211123
我期待 output 就像UNION ALL
一樣。 像下面
SELECT JSON_VALUE(j.value,'$.AEDAT') FROM OPENJSON(@json,'$.value') AS j
UNION ALL
SELECT JSON_VALUE(j.value,'$.ERDAT') FROM OPENJSON(@json,'$.value') AS j
我錯過了什么? 請建議。
您可以使用OPENJSON
兩次,一次打開數組,再次取消旋轉鍵。 然后只需按您的表變量過濾
DECLARE @col_table TABLE (ColumnName varchar(100) COLLATE Latin1_General_BIN2 PRIMARY KEY)
INSERT INTO @col_table (ColumnName)
SELECT value
FROM STRING_SPLIT(@ColumnName,',');
SELECT
ROW_NUMBER() OVER (ORDER BY (SELECT NULL)),
j2.[key],
j2.value
FROM OPENJSON(@json, '$.value') j1
CROSS APPLY OPENJSON(j1.value) j2
WHERE CAST(j2.[key] AS varchar(100)) IN (
SELECT c.ColumnName
FROM @col_table c
);
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