getschema("foreignkeys") against SqlClient doesn't yield enough information - sql

Question

I need two tables and two sets of fields, not the name of the foreign key and one of the table names. Does anyone know how to query SQL Server for complete foreign key information? Thanks!

Answer 1

This can be an involved venture. The GetSchema as well as INFORMATION_SCHEMA views are incomplete, leading to the need to query the sys views directly for authoritive info.
try running this against your db and learn what you can.
This is from a thought experiment that got out of hand ;-)
BEGIN -- Get a table full of PK and UQ columns
DECLARE #tbl_unique_key_columns TABLE ( -- contains PK and UQ indexes
table_schema NVARCHAR(128),
table_name NVARCHAR(128),
index_name NVARCHAR(128),
column_id INT,
column_name NVARCHAR(128),
is_primary_key BIT,
is_unique_constraint BIT,
is_unique BIT,
is_nullable BIT,
is_rowguidcol BIT,
is_identity BIT,
default_definition NVARCHAR(MAX),
user_type NVARCHAR(128),
table_object_id INT )
INSERT INTO #tbl_unique_key_columns ( table_schema, table_name, index_name, column_id, column_name, is_primary_key, is_unique_constraint, is_unique, is_nullable, is_rowguidcol, is_identity, default_definition, user_type, table_object_id )
-- selects PK and UQ indexes
SELECT S.name AS schema_name, T.name AS table_name, IX.name AS index_name, IC.column_id, C.name AS column_name, IX.is_primary_key, IX.is_unique_constraint, IX.is_unique, C.is_nullable, C.is_rowguidcol, C.is_identity, d.definition, tp.NAME, T.[object_id]
FROM sys.tables AS T
INNER JOIN sys.schemas AS S
ON T.schema_id = S.schema_id
INNER JOIN sys.indexes AS IX
ON T.object_id = IX.object_id
INNER JOIN sys.index_columns AS IC
ON IX.object_id = IC.object_id
AND IX.index_id = IC.index_id
INNER JOIN sys.columns AS C
ON IC.column_id = C.column_id
AND IC.object_id = C.OBJECT_ID
INNER JOIN sys.types AS tp
ON C.user_type_id = tp.user_type_id
LEFT OUTER JOIN sys.default_constraints AS d
ON T.object_id = d.parent_object_id
AND C.column_id = d.parent_column_id
WHERE ( IX.is_unique = 1 )
AND ( IX.is_unique = 1 )
ORDER BY schema_name, table_name, index_name, C.column_id
END
BEGIN -- Get a table full of FK columns
DECLARE #tbl_foreign_key_columns TABLE ( constraint_name NVARCHAR(128),
base_schema_name NVARCHAR(128),
base_table_name NVARCHAR(128),
base_column_id INT,
base_column_name NVARCHAR(128),
unique_schema_name NVARCHAR(128),
unique_table_name NVARCHAR(128),
unique_column_id INT,
unique_column_name NVARCHAR(128),
base_object_id INT,
unique_object_id INT )
INSERT INTO #tbl_foreign_key_columns ( constraint_name, base_schema_name, base_table_name, base_column_id, base_column_name, unique_schema_name, unique_table_name, unique_column_id, unique_column_name, base_object_id, unique_object_id )
SELECT FK.name AS constraint_name, S.name AS base_schema_name, T.name AS base_table_name, C.column_id AS base_column_id, C.name AS base_column_name, US.name AS unique_schema_name, UT.name AS unique_table_name, UC.column_id AS unique_column_id, UC.name AS unique_column_name, T.[object_id], UT.[object_id]
FROM sys.tables AS T
INNER JOIN sys.schemas AS S
ON T.schema_id = S.schema_id
INNER JOIN sys.foreign_keys AS FK
ON T.object_id = FK.parent_object_id
INNER JOIN sys.foreign_key_columns AS FKC
ON FK.object_id = FKC.constraint_object_id
INNER JOIN sys.columns AS C
ON FKC.parent_object_id = C.object_id
AND FKC.parent_column_id = C.column_id
INNER JOIN sys.columns AS UC
ON FKC.referenced_object_id = UC.object_id
AND FKC.referenced_column_id = UC.column_id
INNER JOIN sys.tables AS UT
ON FKC.referenced_object_id = UT.object_id
INNER JOIN sys.schemas AS US
ON UT.schema_id = US.schema_id
ORDER BY base_schema_name, base_table_name
END
SELECT * FROM #tbl_unique_key_columns
SELECT * from #tbl_foreign_key_columns