Question

I have a table it is called “Users”

Users table has UserId as a primary key and it is a foreign key for other 15 tables.

Is there a query template which will select top 200 rows from users and all related tables in one shot? So i will not need to type all other 15 tables in the query.

Would Query dynamically find and bring columns from related tables?

It can use inner join for all relations between tables.

Answer 1

I will admit that this is super ugly and probably needs lots more work, but it does the basic query generation based on PK/FK relations. You should probably change inner join to left join, if any of the FK tables can be missing corresponding PK records.

declare @table varchar(50);
set @table = 'Users';

declare @pk_table varchar(50);
declare @fk_table varchar(50);
declare @pk_column varchar(50);
declare @fk_column varchar(50);
declare @curr_table varchar(50);
set @curr_table = '';

declare @sql varchar(8000);
set @sql = 'select top 200 * from ' + @table + char(10)
DECLARE table_cursor CURSOR FOR 
SELECT
    K_Table = FK.TABLE_NAME,
    FK_Column = CU.COLUMN_NAME,
    PK_Table = PK.TABLE_NAME,
    PK_Column = PT.COLUMN_NAME--,
    --Constraint_Name = C.CONSTRAINT_NAME
FROM
    INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK
    ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK
    ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU
    ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME
INNER JOIN (
            SELECT
                i1.TABLE_NAME,
                i2.COLUMN_NAME
            FROM
                INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1
            INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2
                ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME
            WHERE
                i1.CONSTRAINT_TYPE = 'PRIMARY KEY'
           ) PT
    ON PT.TABLE_NAME = PK.TABLE_NAME
where PK.TABLE_NAME = @table   

OPEN table_cursor
FETCH NEXT FROM table_cursor INTO @fk_table, @fk_column, @pk_table, @pk_column

WHILE @@FETCH_STATUS = 0
BEGIN
    if @curr_table <> @fk_table
    begin
        -- create join
        set @sql = @sql + ' inner join ' + @fk_table + char(10)
        set @sql = @sql + ' on ' + @pk_table + '.' + @pk_column + ' = ' + @fk_table + '.' + @fk_column + char(10)
    end
    else
    begin
        -- create join on fields
        set @sql = @sql + ' and ' + @pk_table + '.' + @pk_column + ' = ' + @fk_table + '.' + @fk_column + char(10)
    end
FETCH NEXT FROM table_cursor INTO @fk_table, @fk_column, @pk_table, @pk_column
END

CLOSE table_cursor
DEALLOCATE table_cursor

print @sql