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Finding SQL Database Type for Custom Type

I work with an outdated database that has a large number of custom SQL types. I am writing a method in .NET in which I define parameters in a SqlParameter object. I need basic SQL types for custom types in order to correctly define parameters when I dynamically create them at runtime.

For this, I created this procedure:

(@typename sysname)  

AS  

SET NOCOUNT ON  

SELECT distinct
st.name as UserType,
t.precision, t.max_length,
bt.name as BaseType
FROM
dbo.syscolumns c
INNER JOIN dbo.systypes st ON st.xusertype = c.xusertype
INNER JOIN dbo.systypes bt ON bt.xusertype = c.xtype
inner join sys.types t on st.name = t.name
WHERE
st.name = 'bVendor'

I am wondering if this is the best way to get the base type of a type for a user-defined type?

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2 answers

systypes syscolumns - , sys.types sys.columns , , SQL Server 2000+ ( ).

, :

SELECT name, precision, scale, max_length
  FROM sys.types AS t
  WHERE name = 'bVendor';

:

SELECT name, precision, scale, max_length
  FROM sys.types AS t
  WHERE is_user_defined = 1;

( ) :

UPDATE, :

SELECT 
  [column] = c.name, 
  [base type] = COALESCE(bt.name, t.name),
  [defined type] = t.name, 
  t.precision, 
  t.scale, 
  t.max_length
FROM sys.columns AS c
INNER JOIN sys.types AS t
ON c.system_type_id = t.system_type_id
AND c.user_type_id = t.user_type_id
LEFT OUTER JOIN sys.types AS bt
ON t.is_user_defined = 1
AND bt.is_user_defined = 0
AND t.system_type_id = bt.system_type_id
AND t.user_type_id <> bt.user_type_id
WHERE c.object_id = OBJECT_ID('dbo.your_table_name');

, , (, CREATE TYPE blat FROM nvarchar(32);). ( , ), join :

ON t.is_user_defined = 1
AND bt.is_user_defined = 0
AND t.system_type_id = bt.system_type_id
AND bt.user_type_id = bt.system_type_id
+7

, INFORMATION_SCHEMA.DOMAINS:

SELECT 
   DOMAIN_SCHEMA,
   DOMAIN_NAME,
   DATA_TYPE,
   NUMERIC_PRECISION,
   NUMERIC_SCALE,
   DATETIME_PRECISION,
   CHARACTER_MAXIMUM_LENGTH

FROM 
   INFORMATION_SCHEMA.DOMAINS

UPD: :

  SELECT 
     DOMAIN_SCHEMA + '.' + DOMAIN_NAME AS TypeName,
     DATA_TYPE + 
        COALESCE('('+ 
           CAST(COALESCE(NUMERIC_PRECISION,DATETIME_PRECISION,CHARACTER_MAXIMUM_LENGTH) AS VARCHAR) + 
           COALESCE(',' + CAST(NUMERIC_SCALE AS VARCHAR),'') +
        ')','') AS Definition

  FROM 
  (
     SELECT 
        DOMAIN_SCHEMA,
        DOMAIN_NAME,
        DATA_TYPE,
        CASE 
           WHEN DATA_TYPE IN ('tinyint','smallint','int','bigint') THEN NULL
           ELSE NUMERIC_PRECISION
        END AS NUMERIC_PRECISION,
        NUMERIC_SCALE,
        CASE 
           WHEN DATA_TYPE IN ('smalldatetime','datetime','date') THEN NULL
           ELSE DATETIME_PRECISION
        END AS DATETIME_PRECISION,
        CHARACTER_MAXIMUM_LENGTH

     FROM 
        INFORMATION_SCHEMA.DOMAINS
  ) T

( , )

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