現貨的差異簡單的方法是省略WITH
部分
原始查詢:
DECLARE @prmInputData NVARCHAR(MAX) = '{ "a": { "b": 1, "c": 2 } }';
SELECT *
FROM OPENJSON(@prmInputData, '$')
WITH (
b INT '$.a.b',
c INT '$.a.c',
a NVARCHAR(MAX) '$.a' AS JSON
);
SELECT *
FROM OPENJSON(@prmInputData, '$.a')
WITH (
b INT '$.b',
c INT '$.c',
a NVARCHAR(MAX) '$' AS JSON
);
輸出:
╔═══╦═══╦════════════════════╗
║ b ║ c ║ a ║
╠═══╬═══╬════════════════════╣
║ 1 ║ 2 ║ { "b": 1, "c": 2 } ║
╚═══╩═══╩════════════════════╝
vs
╔═══╦═══╦══════╗
║ b ║ c ║ a ║
╠═══╬═══╬══════╣
║ 1 ║ 2 ║ NULL ║
╚═══╩═══╩══════╝
去除WITH
後:
DECLARE @prmInputData NVARCHAR(MAX) = '{ "a": { "b": 1, "c": 2 } }';
SELECT *
FROM OPENJSON(@prmInputData, '$');
SELECT *
FROM OPENJSON(@prmInputData, '$.a');
結果:
╔═════╦════════════════════╦══════╗
║ key ║ value ║ type ║
╠═════╬════════════════════╬══════╣
║ a ║ { "b": 1, "c": 2 } ║ 5 ║ -- 5 ObjectValue
╚═════╩════════════════════╩══════╝
vs
╔═════╦═══════╦══════╗
║ key ║ value ║ type ║
╠═════╬═══════╬══════╣
║ b ║ 1 ║ 2 ║ -- 2 IntValue
║ c ║ 2 ║ 2 ║ -- 2 IntValue
╚═════╩═══════╩══════╝
現在你可以檢查有路徑的行爲'$.a'
VS '$'
。
從OPENJSON:
If you want to return a nested JSON fragment from a JSON property, you have to provide the AS JSON flag. Without this option, if the property can't be found, OPENJSON returns a NULL value instead of the referenced JSON object or array, or it returns a run-time error in strict mode .
那麼嚴格的方式試圖第二:
DECLARE @prmInputData NVARCHAR(MAX) = '{ "a": { "b": 1, "c": 2 } }';
SELECT *
FROM OPENJSON(@prmInputData, '$.a')
WITH (
b INT '$.b',
c INT '$.c',
a NVARCHAR(MAX) 'strict $' AS JSON
);
這將結束與錯誤:
Property cannot be found on the specified JSON path.
啊真有意思,謝謝。那麼有什麼辦法可以像我想在同一個OPENJSON查詢中一樣選擇多個圖層嗎? – NightCabbage