SQL Server 【应用】JSON

本文主要是介绍SQL Server 【应用】JSON，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

摘要

不建议在sql中使用json，但是json在sql中确实有很多灵活的使用，尤其是复杂查询，记录一下常见的使用情况

16版本下支持json

SQL Server 2016开始支持JSON数据类型，现在很多还是没有升级到这个版本，为了支持json，需要自己定义json处理函数

附上处理json的函数

CREATE FUNCTION [dbo].[ParseJSON]( @json nvarchar(max) ) 
RETURNS @hierarchy table 
( 
object_id int NOT NULL, /* [0 -- Not an object] each list or object has an object id. This ties all elements to a parent. Lists are treated as objects here */ 
parent_id int NOT NULL, /* [0 -- Root] if the element has a parent then it is in this column. The document is the ultimate parent, so you can get the structure from recursing from the document */ 
name nvarchar(2000), /* the name of the object */ 
stringvalue nvarchar(4000) NOT NULL, /*the string representation of the value of the element. */ 
valuetype nvarchar(100) NOT NULL, /* the declared type of the value represented as a string in stringvalue*/ 
bigintvalue bigint, 
boolvalue bit 
) 

AS 

BEGIN 
DECLARE 
@firstobject int, --the index of the first open bracket found in the JSON string 
@opendelimiter int, --the index of the next open bracket found in the JSON string 
@nextopendelimiter int,--the index of subsequent open bracket found in the JSON string 
@nextclosedelimiter int,--the index of subsequent close bracket found in the JSON string 
@type nvarchar(10),--whether it denotes an object or an array 
@nextclosedelimiterChar CHAR(1),--either a '}' or a ']' 
@contents nvarchar(MAX), --the unparsed contents of the bracketed expression 
@start int, --index of the start of the token that you are parsing 
@end int,--index of the end of the token that you are parsing 
@param int,--the parameter at the end of the next Object/Array token 
@endofname int,--the index of the start of the parameter at end of Object/Array token 
@token nvarchar(4000),--either a string or object 
@value nvarchar(MAX), -- the value as a string 
@name nvarchar(200), --the name as a string 
@parent_id int,--the next parent ID to allocate 
@lenjson int,--the current length of the JSON String 
@characters NCHAR(62),--used to convert hex to decimal 
@result BIGINT,--the value of the hex symbol being parsed 
@index SMALLINT,--used for parsing the hex value 
@escape int; --the index of the next escape character 

/* in this temporary table we keep all strings, even the names of the elements, since they are 'escaped' 
* in a different way, and may contain, unescaped, brackets denoting objects or lists. These are replaced in 
* the JSON string by tokens representing the string 
*/ 
DECLARE @strings table 
( 
string_id int IDENTITY(1, 1), 
stringvalue nvarchar(MAX) 
) 

/* initialise the characters to convert hex to ascii */ 
SET @characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; 
SET @parent_id = 0; 

/* firstly we process all strings. This is done because [{} and ] aren't escaped in strings, which complicates an iterative parse. */ 
WHILE 1 = 1 /* forever until there is nothing more to do */ 
BEGIN 
SET @start = PATINDEX('%[^a-zA-Z]["]%', @json collate SQL_Latin1_General_CP850_Bin); /* next delimited string */ 

IF @start = 0 BREAK; /*no more so drop through the WHILE loop */ 

IF SUBSTRING(@json, @start+1, 1) = '"' 
BEGIN /* Delimited name */ 
SET @start = @start+1; 
SET @end = PATINDEX('%[^\]["]%', RIGHT(@json, LEN(@json+'|')-@start) collate SQL_Latin1_General_CP850_Bin); 
END 

IF @end = 0 /*no end delimiter to last string*/ 
BREAK; /* no more */ 

SELECT @token = SUBSTRING(@json, @start+1, @end-1) 

/* now put in the escaped control characters */ 
SELECT @token = REPLACE(@token, from_string, to_string) 
FROM 
( 
SELECT '\"' AS from_string, '"' AS to_string 
UNION ALL 
SELECT '\\', '\' 
UNION ALL 
SELECT '\/', '/' 
UNION ALL 
SELECT '\b', CHAR(08) 
UNION ALL 
SELECT '\f', CHAR(12) 
UNION ALL 
SELECT '\n', CHAR(10) 
UNION ALL 
SELECT '\r', CHAR(13) 
UNION ALL 
SELECT '\t', CHAR(09) 
) substitutions; 

SET @result = 0; 
SET @escape = 1; 

/*Begin to take out any hex escape codes*/ 
WHILE @escape > 0 
BEGIN 

/* find the next hex escape sequence */ 
SET @index = 0; 
SET @escape = PATINDEX('%\x[0-9a-f][0-9a-f][0-9a-f][0-9a-f]%', @token collate SQL_Latin1_General_CP850_Bin); 

IF @escape > 0 /* if there is one */ 
BEGIN 

WHILE @index < 4 /* there are always four digits to a \x sequence */ 
BEGIN 
/* determine its value */ 
SET @result = @result + POWER(16, @index) * (CHARINDEX(SUBSTRING(@token, @escape + 2 + 3 - @index, 1), @characters) - 1); 
SET @index = @index + 1; 
END 

/* and replace the hex sequence by its unicode value */ 
SET @token = STUFF(@token, @escape, 6, NCHAR(@result)); 
END 

END 

/* now store the string away */ 
INSERT INTO @strings (stringvalue) SELECT @token; 

/* and replace the string with a token */ 
SET @json = STUFF(@json, @start, @end + 1, '@string' + CONVERT(nvarchar(5), @@identity)); 

END 

/* all strings are now removed. Now we find the first leaf. */ 
WHILE 1 = 1 /* forever until there is nothing more to do */ 
BEGIN 

SET @parent_id = @parent_id + 1; 

/* find the first object or list by looking for the open bracket */ 
SET @firstobject = PATINDEX('%[{[[]%', @json collate SQL_Latin1_General_CP850_Bin); /*object or array*/ 

IF @firstobject = 0 BREAK; 

IF (SUBSTRING(@json, @firstobject, 1) = '{') 
SELECT @nextclosedelimiterChar = '}', @type = 'object'; 
ELSE 
SELECT @nextclosedelimiterChar = ']', @type = 'array'; 


SET @opendelimiter = @firstobject; 

WHILE 1 = 1 --find the innermost object or list... 
BEGIN 
SET @lenjson = LEN(@json+'|') - 1; 

/* find the matching close-delimiter proceeding after the open-delimiter */ 
SET @nextclosedelimiter = CHARINDEX(@nextclosedelimiterChar, @json, @opendelimiter + 1); 

/* is there an intervening open-delimiter of either type */ 
SET @nextopendelimiter = PATINDEX('%[{[[]%',RIGHT(@json, @lenjson-@opendelimiter) collate SQL_Latin1_General_CP850_Bin); /*object*/ 

IF @nextopendelimiter = 0 BREAK; 

SET @nextopendelimiter = @nextopendelimiter + @opendelimiter; 

IF @nextclosedelimiter < @nextopendelimiter BREAK; 

IF SUBSTRING(@json, @nextopendelimiter, 1) = '{' 
SELECT @nextclosedelimiterChar = '}', @type = 'object'; 
ELSE 
SELECT @nextclosedelimiterChar = ']', @type = 'array'; 

SET @opendelimiter = @nextopendelimiter; 
END 

/* and parse out the list or name/value pairs */ 
SET @contents = SUBSTRING(@json, @opendelimiter+1, @nextclosedelimiter-@opendelimiter - 1); 

SET @json = STUFF(@json, @opendelimiter, @nextclosedelimiter - @opendelimiter + 1, '@' + @type + CONVERT(nvarchar(5), @parent_id)); 

WHILE (PATINDEX('%[A-Za-z0-9@+.e]%', @contents collate SQL_Latin1_General_CP850_Bin)) < > 0 
BEGIN /* WHILE PATINDEX */ 

IF @type = 'object' /*it will be a 0-n list containing a string followed by a string, number,boolean, or null*/ 
BEGIN 

SET @end = CHARINDEX(':', ' '+@contents); /*if there is anything, it will be a string-based name.*/ 
SET @start = PATINDEX('%[^A-Za-z@][@]%', ' ' + @contents collate SQL_Latin1_General_CP850_Bin); /*AAAAAAAA*/ 

SET @token = SUBSTRING(' '+@contents, @start + 1, @end - @start - 1); 
SET @endofname = PATINDEX('%[0-9]%', @token collate SQL_Latin1_General_CP850_Bin); 
SET @param = RIGHT(@token, LEN(@token)-@endofname + 1); 

SET @token = LEFT(@token, @endofname - 1); 
SET @contents = RIGHT(' ' + @contents, LEN(' ' + @contents + '|') - @end - 1); 

SELECT @name = stringvalue FROM @strings WHERE string_id = @param; /*fetch the name*/ 

END 
ELSE 
BEGIN 
SET @name = null; 
END 

SET @end = CHARINDEX(',', @contents); /*a string-token, object-token, list-token, number,boolean, or null*/ 

IF @end = 0 
SET @end = PATINDEX('%[A-Za-z0-9@+.e][^A-Za-z0-9@+.e]%', @contents+' ' collate SQL_Latin1_General_CP850_Bin) + 1; 

SET @start = PATINDEX('%[^A-Za-z0-9@+.e][A-Za-z0-9@+.e]%', ' ' + @contents collate SQL_Latin1_General_CP850_Bin); 

/*select @start,@end, LEN(@contents+'|'), @contents */ 

SET @value = RTRIM(SUBSTRING(@contents, @start, @end-@start)); 
SET @contents = RIGHT(@contents + ' ', LEN(@contents+'|') - @end); 

IF SUBSTRING(@value, 1, 7) = '@object' 
INSERT INTO @hierarchy (name, parent_id, stringvalue, object_id, valuetype) 
SELECT @name, @parent_id, SUBSTRING(@value, 8, 5), SUBSTRING(@value, 8, 5), 'object'; 

ELSE 
IF SUBSTRING(@value, 1, 6) = '@array' 
INSERT INTO @hierarchy (name, parent_id, stringvalue, object_id, valuetype) 
SELECT @name, @parent_id, SUBSTRING(@value, 7, 5), SUBSTRING(@value, 7, 5), 'array'; 
ELSE 
IF SUBSTRING(@value, 1, 7) = '@string' 
INSERT INTO @hierarchy (name, parent_id, stringvalue, valuetype, object_id) 
SELECT @name, @parent_id, stringvalue, 'string', 0 
FROM @strings 
WHERE string_id = SUBSTRING(@value, 8, 5); 
ELSE 
IF @value IN ('true', 'false') 
INSERT INTO @hierarchy (name, parent_id, stringvalue, valuetype, object_id, boolvalue) 
SELECT @name, @parent_id, @value, 'boolean', 0, CASE @value WHEN 'true' THEN 1 ELSE 0 END; 
ELSE 
IF @value = 'null' 
INSERT INTO @hierarchy (name, parent_id, stringvalue, valuetype, object_id) 
SELECT @name, @parent_id, @value, 'null', 0; 
ELSE 
IF PATINDEX('%[^0-9]%', @value collate SQL_Latin1_General_CP850_Bin) > 0 
INSERT INTO @hierarchy (name, parent_id, stringvalue, valuetype, object_id) 
SELECT @name, @parent_id, @value, 'real', 0; 
ELSE 
INSERT INTO @hierarchy (name, parent_id, stringvalue, valuetype, object_id, bigintvalue)
SELECT @name, @parent_id, @value, 'bigint', 0, CONVERT(BIGINT,@value);

END /* WHILE PATINDEX */ 

END /* WHILE 1=1 forever until there is nothing more to do */ 

INSERT INTO @hierarchy (name, parent_id, stringvalue, object_id, valuetype) 
SELECT '', 0, '', @parent_id - 1, @type; 

RETURN; 

END

用这个函数去处理json字符串，转成二维表，会有父子节点，数据类型等相关信息

declare @json varchar(max) = '{"data":{"name":"tom","code":"Tom","age":12}}'

select * from parseJSON(@json) where name = 'code'

表格json处理

遇到一个有意思的查询条件，是根据两个字段的组合来查询数据

例如公司+项目，传过来的是这样的json数据

[
    {
        "company":"alibaba",
        "project":["A","B"]
    },
    {
        "company":"tencent",
        "project":["B","C"]
    },
    {
        "company":"bytedance",
        "project":["A","C"]
    }
]

对于这样的查询刚开始的想法就是每个条件查出来后Union所有的查询结果，然而还需要分页，外面还需要再套一层，麻烦，就想着在数据库自己处理json的查询条件，将这些条件放到临时表里，直接关联主表就很方便了

还是需要先转一下json的格式，转成二维表

[
    {
        "company":"alibaba",
        "project":"A"
    },
     {
        "company":"alibaba",
        "project":"B"
    },
    {
        "company":"tencent",
        "project":"B"
    },
    {
        "company":"tencent",
        "project":"C"
    },
    {
        "company":"bytedance",
        "project":"A"
    },
    {
        "company":"bytedance",
        "project":"C"
    }
]

这样的数据parseJSON后的格式是这样的，还需要进行行列转换一下

转化之后就可以很清楚的看到表结构了，直接用主表去做关联就可以了，很方便

这篇关于SQL Server 【应用】JSON的文章就介绍到这儿，希望我们推荐的文章对大家有所帮助，也希望大家多多支持为之网！