8.14.1. JSON Input and Output Syntax

8.14.1. JSON Input and Output Syntax8.14.1.JSON输入和输出语法The input/output syntax for the JSON data types is as specified in RFC 7159.RFC 7159定义了JSON数据类型的输入和输出语法。The following are all valid jso...

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丹心明月 · 2020-03-09 17:08:20 发布

8.14.1. JSON Input and Output Syntax

8.14.1.JSON输入和输出语法

The input/output syntax for the JSON data types is as specified in RFC 7159.

RFC 7159定义了JSON数据类型的输入和输出语法。

The following are all valid json (or jsonb) expressions:

以下为json（或jsonb）可用的表达式：

-- Simple scalar/primitive value

-- Primitive values can be numbers, quoted strings, true, false, or

null

SELECT '5'::json;

-- Array of zero or more elements (elements need not be of same type)

SELECT '[1, 2, "foo", null]'::json;

-- Object containing pairs of keys and values

-- Note that object keys must always be quoted strings

SELECT '{"bar": "baz", "balance": 7.77, "active": false}'::json;

-- Arrays and objects can be nested arbitrarily

SELECT '{"foo": [true, "bar"], "tags": {"a": 1, "b": null}}'::json;

As previously stated, when a JSON value is input and then printed without any additional processing,json outputs the same text that was input, while jsonb does not preserve semantically-insignificant details such as whitespace. For example, note the differences here:

如前所述，当输入JSON值然后在不进行任何其他处理的情况下进行输出时，json将输出与输入相同的文本，而jsonb不会保留语义上无关紧要的细节，例如空格。例如，请注意此处的区别：

SELECT '{"bar": "baz", "balance": 7.77, "active":false}'::json;

json

-------------------------------------------------

{"bar": "baz", "balance": 7.77, "active":false}

(1 row)

SELECT '{"bar": "baz", "balance": 7.77, "active":false}'::jsonb;

jsonb

--------------------------------------------------

{"bar": "baz", "active": false, "balance": 7.77}

(1 row)

One semantically-insignificant detail worth noting is that in jsonb, numbers will be printed according to the behavior of the underlying numeric type. In practice this means that numbers entered with E notation will be printed without it, for example:

值得注意的一个语义无关紧要的细节是，在jsonb中，数字将根据基础数字类型的行为进行打印。实际上，这意味着使用E记号输入的数字将以普通格式打印，例如：

SELECT '{"reading": 1.230e-5}'::json, '{"reading":1.230e-5}'::jsonb;

json | jsonb

-----------------------+-------------------------

{"reading": 1.230e-5} | {"reading": 0.00001230}

(1 row)

However, jsonb will preserve trailing fractional zeroes, as seen in this example, even though those are semantically insignificant for purposes such as equality checks.

但是，jsonb将保留尾随零，如本例所示，即使它们在语义上无意义（例如，相等性检查）也是如此。