Is it a good idea to use COLUMN AS (left([Another_Column],(4)) instead of LEFT in the select?Which 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 keyReclaim space from dropped column in SQLServer2008R2Int for identity/primary key and Guid for public identifier, best practices?
Delete n lines skip 1 line script
Incomplete iffalse: How to shift a scope in polar coordinate?
How do I automatically add linebreaks "\" to the end of each row of a tabular environment?
IEEE 754 square root with Newton-Raphson
How do we know neutrons have no charge?
Detail vs. filler
How to work around players whose backstory goes against the story?
What could cause lower torque than normal during cruise in a King Air 300?
Isn't the detector always measuring, and thus always collapsing the state?
Would a 737 pilot use flaps in nose dive?
Why does JSON parsing not fail on the first character for strings starting with "t"?
Is it good to engage in exceptional cases where it is permissible to do a typically forbidden action to which one has a taivah for
How to study endgames?
How is the Apple Watch ECG disabled in certain countries?
If a spaceship ran out of fuel somewhere in space between Earth and Mars, does it slowly drift off to the Sun?
What does it mean by "my days-of-the-week underwear only go to Thursday" in this context?
Are devices supposed to automatically be removed from iCloud when all content and settings are erased?
Is there an in-universe explanation of how Frodo's arrival in Valinor was recorded in the Red Book?
Is it possible to take a database offline when doing a backup using an SQL job?
Calculate the Ultraradical
Why does `FindFit` fail so badly in this simple case?
Should I be an author on another PhD student's paper if I went to their meetings and gave advice?
Is it possible for a company to grow but its stock price stays the same or decrease?
How to add the real hostname in the beginning of Linux cli command
Is it a good idea to use COLUMN AS (left([Another_Column],(4)) instead of LEFT in the select?
Which 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 keyReclaim space from dropped column in SQLServer2008R2Int for identity/primary key and Guid for public identifier, best practices?
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;
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
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
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
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 Mar 28 at 19:41
Josh Darnell
13.6k4 gold badges31 silver badges63 bronze badges
13.6k4 gold badges31 silver badges63 bronze badges
asked Mar 28 at 12:48
Racer SQLRacer SQL
3,5015 gold badges31 silver badges74 bronze badges
3,5015 gold badges31 silver badges74 bronze badges
add a comment
|
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".
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.
add a comment
|
Your Answer
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "182"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/4.0/"u003ecc by-sa 4.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fdba.stackexchange.com%2fquestions%2f233382%2fis-it-a-good-idea-to-use-column-as-leftanother-column-4-instead-of-left-i%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
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".
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".
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".
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 Mar 28 at 12:49
Erik DarlingErik Darling
27.6k13 gold badges84 silver badges139 bronze badges
27.6k13 gold badges84 silver badges139 bronze badges
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.
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.
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.
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 Mar 28 at 19:40
Josh DarnellJosh Darnell
13.6k4 gold badges31 silver badges63 bronze badges
13.6k4 gold badges31 silver badges63 bronze badges
add a comment
|
add a comment
|
Thanks for contributing an answer to Database Administrators Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fdba.stackexchange.com%2fquestions%2f233382%2fis-it-a-good-idea-to-use-column-as-leftanother-column-4-instead-of-left-i%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown