到目前为止，我发现的所有其他内容都只是指向 sys.columns 并返回有关该列的一些元数据。但是，我希望此信息采用可用于动态 SQL 的格式，以便在另一个表中创建相同的列。
我遇到的主要问题是对于 int 或 bit 等类型，它们不允许列宽，sys.columns 仍然显示长度、精度或比例（在 datetime 的情况下全部 3 )。
有没有办法从列元数据中获取可用类型？例如，给定列名，我希望结果返回为 int 或 decimal(5,2) 等。
【问题讨论】：
标签： sql-server
从 Louis Davidson 那里偷东西：Utility Queries–Column Metadata - Louis Davidson
SELECT *
FROM ( SELECT REPLACE(LOWER(objects.type_desc), '_', ' ') AS table_type, schemas.name AS schema_name, objects.name AS table_name,
columns.name AS column_name, CASE WHEN columns.is_identity = 1 THEN 'IDENTITY NOT NULL'
WHEN columns.is_nullable = 1 THEN 'NULL'
ELSE 'NOT NULL'
END AS nullability,
--types that have a ascii character or binary length
CASE WHEN columns.is_computed = 1 THEN 'Computed'
WHEN types.name IN ( 'varchar', 'char', 'varbinary' ) THEN types.name +
CASE WHEN columns.max_length = -1 THEN '(max)'
ELSE '(' + CAST(columns.max_length AS VARCHAR(4)) + ')' END
--types that have an unicode character type that requires length to be halved
WHEN types.name IN ( 'nvarchar', 'nchar' ) THEN types.name +
CASE WHEN columns.max_length = -1 THEN '(max)'
ELSE '(' + CAST(columns.max_length / 2 AS VARCHAR(4)) + ')'
END
--types with a datetime precision
WHEN types.name IN ( 'time', 'datetime2', 'datetimeoffset' ) THEN types.name +
'(' + CAST(columns.scale AS VARCHAR(4)) + ')'
--types with a precision/scale
WHEN types.name IN ( 'numeric', 'decimal' )
THEN types.name + '(' + CAST(columns.precision AS VARCHAR(4)) + ',' +
CAST(columns.scale AS VARCHAR(4)) + ')'
--timestamp should be reported as rowversion
WHEN types.name = 'timestamp' THEN 'rowversion'
--and the rest. Note, float is declared with a bit length, but is
--represented as either float or real in types
ELSE types.name
END AS declared_datatype,
--types that have a ascii character or binary length
CASE WHEN baseType.name IN ( 'varchar', 'char', 'varbinary' )
THEN baseType.name +
CASE WHEN columns.max_length = -1 THEN '(max)'
ELSE '(' + CAST(columns.max_length AS VARCHAR(4)) + ')'
END
--types that have an unicode character type that requires length to be halved
WHEN baseType.name IN ( 'nvarchar', 'nchar' )
THEN baseType.name +
CASE WHEN columns.max_length = -1 THEN '(max)'
ELSE '(' + CAST(columns.max_length / 2 AS VARCHAR(4)) + ')'
END
--types with a datetime precision
WHEN baseType.name IN ( 'time', 'datetime2', 'datetimeoffset' )
THEN baseType.name + '(' + CAST(columns.scale AS VARCHAR(4)) + ')'
--types with a precision/scale
WHEN baseType.name IN ( 'numeric', 'decimal' )
THEN baseType.name + '(' + CAST(columns.precision AS VARCHAR(4)) +
',' + CAST(columns.scale AS VARCHAR(4)) + ')'
--timestamp should be reported as rowversion
WHEN baseType.name = 'timestamp' THEN 'rowversion'
--and the rest. Note, float is declared with a bit length, but is
--represented as either float or real in types
ELSE baseType.name
END AS base_datatype,
CASE WHEN EXISTS ( SELECT *
FROM sys.key_constraints
JOIN sys.indexes
ON key_constraints.parent_object_id = indexes.object_id
AND key_constraints.unique_index_id = indexes.index_id
JOIN sys.index_columns
ON index_columns.object_id = indexes.object_id
AND index_columns.index_id = indexes.index_id
WHERE key_constraints.type = 'PK'
AND columns.column_id = index_columns.column_id
AND columns.OBJECT_ID = index_columns.OBJECT_ID )
THEN 1
ELSE 0 END AS primary_key_column,
columns.column_id, default_constraints.definition AS default_value,
check_constraints.definition AS column_check_constraint,
CASE WHEN EXISTS ( SELECT *
FROM sys.check_constraints AS cc
WHERE cc.parent_object_id = columns.OBJECT_ID
AND cc.definition LIKE '%~[' + columns.name + '~]%' ESCAPE '~'
AND cc.parent_column_id = 0 ) THEN 1
ELSE 0
END AS table_check_constraint_reference
FROM sys.columns
JOIN sys.types
ON columns.user_type_id = types.user_type_id
JOIN sys.types AS baseType
ON columns.system_type_id = baseType.system_type_id
AND baseType.user_type_id = baseType.system_type_id
JOIN sys.objects
JOIN sys.schemas
ON schemas.schema_id = objects.schema_id
ON objects.object_id = columns.OBJECT_ID
LEFT OUTER JOIN sys.default_constraints
ON default_constraints.parent_object_id = columns.object_id
AND default_constraints.parent_column_id = columns.column_id
LEFT OUTER JOIN sys.check_constraints
ON check_constraints.parent_object_id = columns.object_id
AND check_constraints.parent_column_id = columns.column_id ) AS rows
WHERE table_type = 'user table'
AND schema_name LIKE '%'
AND table_name LIKE '%'
AND column_name LIKE '%'
AND nullability LIKE '%'
AND base_datatype LIKE '%'
AND declared_datatype LIKE '%'
ORDER BY table_type, schema_name, table_name, column_id
【讨论】：