SQL Server table to json

问题:

I am looking to pull some columns (Col1 and 2) of a table and put in JSON format and also write some hardcoded JSON in each node, like this.

{ "col1":"xxxx", "col2":"xxxx", "hardcodedString":"xxxx", "hardcodedString":"xxxx", "hardcodedString":"xxxx", "hardcodedString":"xxxx", "hardcodedString":"xxxx"},

I found the following git script, it creates a SP that should generate JSON but when i executed as required i get 'Commands Completed Succesfully'

Any ideas where the output is going or indeed if a better way to acheive my JSON?

create procedure [dbo].[GetJSON] (
    @schema_name varchar(50),
    @table_name varchar(50),
    @registries_per_request smallint = null
)
as
begin
    if ( ( select count(*) from information_schema.tables where table_schema = @schema_name and table_name = @table_name ) > 0 )
    begin
        declare @json varchar(max),
            @line varchar(max),
            @columns varchar(max),
            @sql nvarchar(max),
            @columnNavigator varchar(50),
            @counter tinyint,
            @size varchar(10)

        if (@registries_per_request is null)
        begin
            set @size = ''
        end
        else
        begin
            set @size = 'top ' + convert(varchar, @registries_per_request)
        end
        set @columns = '{'

        declare schemaCursor cursor for
            select column_name
            from information_schema.columns
            where table_schema = @schema_name
            and table_name = @table_name
        open schemaCursor

        fetch next from schemaCursor into @columnNavigator

        select @counter = count(*)
        from information_schema.columns
        where table_schema = @schema_name
        and table_name = @table_name

        while @@fetch_status = 0
        begin
            set @columns = @columns + '''''' + @columnNavigator + ''''':'''''' + convert(varchar, ' + @columnNavigator + ') + '''''''
            set @counter = @counter - 1
            if ( 0 != @counter )
            begin
                set @columns = @columns + ','
            end

            fetch next from schemaCursor into @columnNavigator
        end 

        set @columns =  @columns + '}'

        close schemaCursor
        deallocate schemaCursor

        set @json = '['

        set @sql = 'select ' + @size + '''' + @columns + ''' as json into tmpJsonTable from [' + @schema_name + '].[' + @table_name + ']'
        exec sp_sqlexec @sql

        select @counter = count(*) from tmpJsonTable

        declare tmpCur cursor for
            select * from tmpJsonTable
        open tmpCur

        fetch next from tmpCur into @line

        while @@fetch_status = 0
        begin
            set @counter = @counter - 1
            set @json = @json + @line
            if ( 0 != @counter )
            begin
                set @json = @json + ','
            end

            fetch next from tmpCur into @line
        end

        set @json = @json + ']'

        close tmpCur
        deallocate tmpCur
        drop table tmpJsonTable

        select @json as json
    end
end

回答1:

I wouldn't really advise it, there are much better ways of doing this in the application layer, but the following avoids loops, and is a lot less verbose than your current method:

CREATE PROCEDURE dbo.GetJSON @ObjectName VARCHAR(255), @registries_per_request smallint = null
AS
BEGIN
    IF OBJECT_ID(@ObjectName) IS NULL
        BEGIN
            SELECT Json = '';
            RETURN
        END;

    DECLARE @Top NVARCHAR(20) = CASE WHEN @registries_per_request IS NOT NULL 
                                    THEN 'TOP (' + CAST(@registries_per_request AS NVARCHAR) + ') ' 
                                    ELSE '' 
                                END;

    DECLARE @SQL NVARCHAR(MAX) = N'SELECT ' + @Top + '* INTO ##T ' + 
                                'FROM ' + @ObjectName;

    EXECUTE SP_EXECUTESQL @SQL;

    DECLARE @X NVARCHAR(MAX) = '[' + (SELECT * FROM ##T FOR XML PATH('')) + ']';


    SELECT  @X = REPLACE(@X, '<' + Name + '>', 
                    CASE WHEN ROW_NUMBER() OVER(ORDER BY Column_ID) = 1 THEN '{'
                         ELSE '' END + Name + ':'),
            @X = REPLACE(@X, '</' + Name + '>', ','),
            @X = REPLACE(@X, ',{', '}, {'),
            @X = REPLACE(@X, ',]', '}]')
    FROM    sys.columns
    WHERE   [Object_ID] = OBJECT_ID(@ObjectName)
    ORDER BY Column_ID;

    DROP TABLE ##T;

    SELECT  Json = @X;

END

N.B. I've changed your two part object name (@schema and @table) to just accept the full object name.

Example on SQL Fiddle

The idea is to basically use the XML extension within SQL-Server to turn the table into XML, then just replace the start tags with {ColumnName: and the end tags with ,. It then requires two more replaces to stop add the closing bracket to the last column of each row, and the remove the final , from the JSON string.

回答2:

Use from the magic words For JSON

example:

 SELECT name, surname  
 FROM emp  
 FOR JSON AUTO  

result:

[{"name": "John"}, {"name": "Jane", "surname": "Doe"}]

more info in:

https://docs.microsoft.com/en-us/sql/relational-databases/json/format-query-results-as-json-with-for-json-sql-server?view=sql-server-2017&viewFallbackFrom=sql-server-2014

回答3:

In ruby using mysql2 gem and json

require 'mysql2'
require 'json'

client = Mysql2::Client.new(:host => "localhost", :username => "user", :password => "your_pass", :database => "db_name")
results = client.query("SELECT col1, col2 FROM table LIMIT 3").to_a

results.each do |res|
  res.merge!({:hardcoded => "xxxx", :hardcoded2 => "xxxxy"})
end

puts JSON.generate results