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Is it a good idea to use COLUMN AS (left([Another_Column],(4)) instead of LEFT in the select?
The Next CEO of Stack OverflowWhich problems arise, declaring the size of all varchar parameters as max in stored proc?How to add/update a column with an incremented value and reset said value based on another column in SQLCan I create a computed column that requires input to select?Can I tell SQL Server not to place data in the buffer cache?Storing NULL versus storing '' in a varchar columnSQL Server - Sudden log autogrowth after database backupProper table design for sparse primary keyWhy did my database size almost double over night?Reclaim space from dropped column in SQLServer2008R2Group by sum based on under group in SQL Server
I came across a table like this:
CREATE TABLE TABLE1
(
CD1 int
,CD2 varchar(16)
,CD3 varchar(21)
,CD4 decimal(14,0)
,CD5 varchar(4)
,CD6 decimal(18,2)
,CD7 AS (left([CD3],(4)))
)
This table has more than 4 BILLION rows (totally unnecessary, but this is another topic).
As you can see in the last column, they use AS (left([CD3],(4))). I think this is pretty useless, since we almost NEVER have a SELECT on this table, and here is just using space.
Isn't it better to select that field during the select when needed?
sql-server sql-server-2008-r2 t-sql
edited 2 hours ago
Josh Darnell
7,25522141
asked 9 hours ago
Racer SQLRacer SQL
3,10142562
add a comment |
I came across a table like this:
CREATE TABLE TABLE1
(
CD1 int
,CD2 varchar(16)
,CD3 varchar(21)
,CD4 decimal(14,0)
,CD5 varchar(4)
,CD6 decimal(18,2)
,CD7 AS (left([CD3],(4)))
)
This table has more than 4 BILLION rows (totally unnecessary, but this is another topic).
As you can see in the last column, they use AS (left([CD3],(4))). I think this is pretty useless, since we almost NEVER have a SELECT on this table, and here is just using space.
Isn't it better to select that field during the select when needed?
sql-server sql-server-2008-r2 t-sql
edited 2 hours ago
Josh Darnell
7,25522141
asked 9 hours ago
Racer SQLRacer SQL
3,10142562
There is a thin chance of getting some more usable statistics. Other than that, probably nothing. But it doesn't use space either :)
– dean
4 hours ago
add a comment |
I came across a table like this:
CREATE TABLE TABLE1
(
CD1 int
,CD2 varchar(16)
,CD3 varchar(21)
,CD4 decimal(14,0)
,CD5 varchar(4)
,CD6 decimal(18,2)
,CD7 AS (left([CD3],(4)))
)
This table has more than 4 BILLION rows (totally unnecessary, but this is another topic).
As you can see in the last column, they use AS (left([CD3],(4))). I think this is pretty useless, since we almost NEVER have a SELECT on this table, and here is just using space.
Isn't it better to select that field during the select when needed?
sql-server sql-server-2008-r2 t-sql
edited 2 hours ago
Josh Darnell
7,25522141
asked 9 hours ago
Racer SQLRacer SQL
3,10142562
I came across a table like this:
CREATE TABLE TABLE1
(
CD1 int
,CD2 varchar(16)
,CD3 varchar(21)
,CD4 decimal(14,0)
,CD5 varchar(4)
,CD6 decimal(18,2)
,CD7 AS (left([CD3],(4)))
)
This table has more than 4 BILLION rows (totally unnecessary, but this is another topic).
As you can see in the last column, they use AS (left([CD3],(4))). I think this is pretty useless, since we almost NEVER have a SELECT on this table, and here is just using space.
Isn't it better to select that field during the select when needed?
sql-server sql-server-2008-r2 t-sql
sql-server sql-server-2008-r2 t-sql
edited 2 hours ago
Josh Darnell
7,25522141
asked 9 hours ago
Racer SQLRacer SQL
3,10142562
edited 2 hours ago
Josh Darnell
7,25522141
asked 9 hours ago
Racer SQLRacer SQL
3,10142562
edited 2 hours ago
Josh Darnell
7,25522141
edited 2 hours ago
Josh Darnell
7,25522141
edited 2 hours ago
Josh Darnell
7,25522141
7,25522141
asked 9 hours ago
Racer SQLRacer SQL
3,10142562
asked 9 hours ago
Racer SQLRacer SQL
3,10142562
asked 9 hours ago
Racer SQLRacer SQL
3,10142562
3,10142562
There is a thin chance of getting some more usable statistics. Other than that, probably nothing. But it doesn't use space either :)
– dean
4 hours ago
add a comment |
There is a thin chance of getting some more usable statistics. Other than that, probably nothing. But it doesn't use space either :)
– dean
4 hours ago
There is a thin chance of getting some more usable statistics. Other than that, probably nothing. But it doesn't use space either :)
– dean
4 hours ago
There is a thin chance of getting some more usable statistics. Other than that, probably nothing. But it doesn't use space either :)
– dean
4 hours ago
add a comment |
2 Answers
2
active
oldest
votes
If the computed column isn't persisted or indexed, it's only a virtual column (expression), and it's not taking up any "space".
answered 9 hours ago
Erik DarlingErik Darling
22.2k1269111
add a comment |
The only reason I can think of for having that column is to index it, because there is some common set of read queries that filter on the first few characters in CD3.
If the computed column is, indeed, indexed, then the it's valuable because:
- it would required less storage than the full 21 char column
- it would incur less page reads for seeks and scans than an index on the full 21 char column
You mentioned the table is rarely read, but I would check for indexes that use this computed column to be sure.
If it's not indexed, then see Erik's answer about the storage aspect of non-persisted computed columns.
answered 2 hours ago
Josh DarnellJosh Darnell
7,25522141
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
If the computed column isn't persisted or indexed, it's only a virtual column (expression), and it's not taking up any "space".
answered 9 hours ago
Erik DarlingErik Darling
22.2k1269111
add a comment |
If the computed column isn't persisted or indexed, it's only a virtual column (expression), and it's not taking up any "space".
answered 9 hours ago
Erik DarlingErik Darling
22.2k1269111
add a comment |
If the computed column isn't persisted or indexed, it's only a virtual column (expression), and it's not taking up any "space".
answered 9 hours ago
Erik DarlingErik Darling
22.2k1269111
If the computed column isn't persisted or indexed, it's only a virtual column (expression), and it's not taking up any "space".
answered 9 hours ago
Erik DarlingErik Darling
22.2k1269111
answered 9 hours ago
Erik DarlingErik Darling
22.2k1269111
answered 9 hours ago
Erik DarlingErik Darling
22.2k1269111
answered 9 hours ago
Erik DarlingErik Darling
22.2k1269111
22.2k1269111
add a comment |
add a comment |
The only reason I can think of for having that column is to index it, because there is some common set of read queries that filter on the first few characters in CD3.
If the computed column is, indeed, indexed, then the it's valuable because:
- it would required less storage than the full 21 char column
- it would incur less page reads for seeks and scans than an index on the full 21 char column
You mentioned the table is rarely read, but I would check for indexes that use this computed column to be sure.
If it's not indexed, then see Erik's answer about the storage aspect of non-persisted computed columns.
answered 2 hours ago
Josh DarnellJosh Darnell
7,25522141
add a comment |
The only reason I can think of for having that column is to index it, because there is some common set of read queries that filter on the first few characters in CD3.
If the computed column is, indeed, indexed, then the it's valuable because:
- it would required less storage than the full 21 char column
- it would incur less page reads for seeks and scans than an index on the full 21 char column
You mentioned the table is rarely read, but I would check for indexes that use this computed column to be sure.
If it's not indexed, then see Erik's answer about the storage aspect of non-persisted computed columns.
answered 2 hours ago
Josh DarnellJosh Darnell
7,25522141
add a comment |
The only reason I can think of for having that column is to index it, because there is some common set of read queries that filter on the first few characters in CD3.
If the computed column is, indeed, indexed, then the it's valuable because:
- it would required less storage than the full 21 char column
- it would incur less page reads for seeks and scans than an index on the full 21 char column
You mentioned the table is rarely read, but I would check for indexes that use this computed column to be sure.
If it's not indexed, then see Erik's answer about the storage aspect of non-persisted computed columns.
answered 2 hours ago
Josh DarnellJosh Darnell
7,25522141
The only reason I can think of for having that column is to index it, because there is some common set of read queries that filter on the first few characters in CD3.
If the computed column is, indeed, indexed, then the it's valuable because:
- it would required less storage than the full 21 char column
- it would incur less page reads for seeks and scans than an index on the full 21 char column
You mentioned the table is rarely read, but I would check for indexes that use this computed column to be sure.
If it's not indexed, then see Erik's answer about the storage aspect of non-persisted computed columns.
answered 2 hours ago
Josh DarnellJosh Darnell
7,25522141
answered 2 hours ago
Josh DarnellJosh Darnell
7,25522141
answered 2 hours ago
Josh DarnellJosh Darnell
7,25522141
answered 2 hours ago
Josh DarnellJosh Darnell
7,25522141
7,25522141
add a comment |
add a comment |
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There is a thin chance of getting some more usable statistics. Other than that, probably nothing. But it doesn't use space either :)
– dean
4 hours ago