Questions tagged [computed-column]

Computed columns are columns that represent a calculation or operation performed on other columns contained in the given table. Known as generated or virtual columns in some products.

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29
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2answers
2k views

Is there a way to prevent Scalar UDFs in computed columns from inhibiting parallelism?

Much has been written about the perils of Scalar UDFs in SQL Server. A casual search will return oodles of results. There are some places where a Scalar UDF is the only option, though. As an ...
18
votes
5answers
4k views

Unable to create a Filtered Index on a Computed Column

In a previous question of mine, Is it a good idea to disable lock escalation while adding new calculated columns to a table?, I am creating a computed column: ALTER TABLE dbo.tblBGiftVoucherItem ADD ...
3
votes
1answer
5k views

Mysql Pivot rows into dynamic columns with unknown number of columns

I have an output of a query as follows: bid | code | amount | ----------------------------- 2915 | BF | -10700.00 | 2915 | YQ | -300.00 | 2915 | YR | 0.00 | 2915 | YM ...
6
votes
1answer
132 views

Table with persisted computed CLR originated data marked with has_unchecked_assembly_data = 1, but DBCC CHECKTABLE does not unset this same flag

We have an OrderLines table with columns: Quantity int not null QtyCancelled int not null QtyBackorder int not null QtyPicking int not null QtyPacking int not null QtyShiped int not null with ...
4
votes
1answer
822 views

Type conversion in expression may affect “CardinalityEstimate” - on a computed column?

I had a look at this question: Type conversion in expression may affect “CardinalityEstimate” in query plan choice? But that was related to collation and not with computed columns. I have the ...
16
votes
2answers
7k views

Why is a NOT NULL computed column considered nullable in a view?

I have a table: CREATE TABLE [dbo].[Realty]( [Id] [int] IDENTITY(1,1) NOT NULL, [RankingBonus] [int] NOT NULL, [Ranking] AS ([Id]+[RankingBonus]) PERSISTED NOT NULL .... ) And a ...
14
votes
2answers
870 views

Computed Column Index Not Used

I want to have a fast lookup based on if two columns are equal. I tried to use a computed column with an index, but SQL Server doesn't seem to use it. If I just use a statically populated bit column ...
5
votes
4answers
821 views

Implicit conversion warning despite persisted computed column vs. performance hit from UDF in persisted computed column definition

I have a need for a computed column to resolve an implicit conversion problem. I have a column that is declared as a VARCHAR that should only ever store integers, but is occasionally populated in ...
5
votes
4answers
593 views

Interpolate dates along a line

I have a road_condition table in Oracle 12c: create table road_condition ( cond_id number(5,0), road_id number(5,0), cond_date date, condition number(5,0) ); insert into ...
5
votes
5answers
4k views

Creating a Persisted Computed Column with a function

I am working with the programmers on a database solution. They want to add a computed column to mimic the old keys for the older queries, procedures, and systems and index it. The new keys will be ...
2
votes
1answer
3k views

How to create a Hash Computed Column for Many Columns?

Does anyone know how to create a Hash Computed Column Persisted? I keep receiving an error below. Otherwise, I will have to utilize an update or trigger statement everytime. I know how to conduct for ...
0
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2answers
47 views

Create integer id columns from existing string columns (integer coding?)

I have an PostgreSQL server with an existing table which has two fixed-width-non-unique-string (variable size) columns such as this: | ID_STRING_A | ID_STRING_B | | 'AAAA' | 'BBBB' | | ...
-1
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2answers
355 views

Create an unique integer id column for an existing string column

I have an PostgreSQL server with an existing table which has an fixed-width-non-unique-string column such as this: | ID_STRING | | 'ABCDEFG' | | 'HIJKLMN' | Now I want to compute integer ids for ...
-4
votes
1answer
121 views

How do I ensure a relationship is commutative and unique? [closed]

In PostgreSQL, we can ensure the relations stored inside a table a commutative-ly (or bidirectional etc) unique. For instance, CREATE TABLE foo ( a int, b int, UNIQUE ( greatest(a,b), least(a,b)...