why I need a dynamic query for “column value from a query”
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For example this returns a value from a query, which I will then use as a column name.
@A=Select top 1 productid from productlist order by timestamp desc
then I would like this "productid" A to be used in the other table
Select @A from customerlist
then the result is @A value instead of field value in customerlist.
When I use dynamic query, I can get right result.
Why?
(I know I can use join but because this productlist table is dynamic, so let's assume it is a sub query)
sql
edited Nov 12 at 4:10
Homam
192
asked Nov 12 at 1:31
NewPy
755
add a comment |
up vote
0
down vote
favorite
For example this returns a value from a query, which I will then use as a column name.
@A=Select top 1 productid from productlist order by timestamp desc
then I would like this "productid" A to be used in the other table
Select @A from customerlist
then the result is @A value instead of field value in customerlist.
When I use dynamic query, I can get right result.
Why?
(I know I can use join but because this productlist table is dynamic, so let's assume it is a sub query)
sql
edited Nov 12 at 4:10
Homam
192
asked Nov 12 at 1:31
NewPy
755
(1) You have a problem with your data model if you have columns that are really data fields. (2) This requires dynamic SQL, so you need to specify the database you are using.
– Gordon Linoff
Nov 12 at 2:00
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
For example this returns a value from a query, which I will then use as a column name.
@A=Select top 1 productid from productlist order by timestamp desc
then I would like this "productid" A to be used in the other table
Select @A from customerlist
then the result is @A value instead of field value in customerlist.
When I use dynamic query, I can get right result.
Why?
(I know I can use join but because this productlist table is dynamic, so let's assume it is a sub query)
sql
edited Nov 12 at 4:10
Homam
192
asked Nov 12 at 1:31
NewPy
755
For example this returns a value from a query, which I will then use as a column name.
@A=Select top 1 productid from productlist order by timestamp desc
then I would like this "productid" A to be used in the other table
Select @A from customerlist
then the result is @A value instead of field value in customerlist.
When I use dynamic query, I can get right result.
Why?
(I know I can use join but because this productlist table is dynamic, so let's assume it is a sub query)
sql
sql
edited Nov 12 at 4:10
Homam
192
asked Nov 12 at 1:31
NewPy
755
edited Nov 12 at 4:10
Homam
192
asked Nov 12 at 1:31
NewPy
755
edited Nov 12 at 4:10
Homam
192
edited Nov 12 at 4:10
Homam
192
edited Nov 12 at 4:10
Homam
192
192
asked Nov 12 at 1:31
NewPy
755
asked Nov 12 at 1:31
NewPy
755
asked Nov 12 at 1:31
NewPy
755
755
(1) You have a problem with your data model if you have columns that are really data fields. (2) This requires dynamic SQL, so you need to specify the database you are using.
– Gordon Linoff
Nov 12 at 2:00
add a comment |
(1) You have a problem with your data model if you have columns that are really data fields. (2) This requires dynamic SQL, so you need to specify the database you are using.
– Gordon Linoff
Nov 12 at 2:00
(1) You have a problem with your data model if you have columns that are really data fields. (2) This requires dynamic SQL, so you need to specify the database you are using.
– Gordon Linoff
Nov 12 at 2:00
(1) You have a problem with your data model if you have columns that are really data fields. (2) This requires dynamic SQL, so you need to specify the database you are using.
– Gordon Linoff
Nov 12 at 2:00
add a comment |
1 Answer
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down vote
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You need "dynamic SQL" because SQL will NOT allow you to use a parameter as a column name or a table name. You can only use parameters for data values such as in a where clause where column1 = @val
set @A = 'çolumn1'
Select @A from customerlist -- this fails because it is not allowed
Dynamic SQL is a "hack" to get around those restrictions as the SQL statement is placed into a string along with any value held by parameters.
set @A = 'çolumn1'
set @SQL = 'Select ' + @A + ' from customerlist;'
execute @SQL -- this works, the SQL statement is valid with no parameters as column names
The string formed as @SQL is a complete sql statement without needing any parameters as column names.
Note: the syntax I used here is incomplete and is based on MS SQL Server, different databases will use a different, but similar, syntax.
answered Nov 12 at 5:08
Used_By_Already
22.3k21838
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
1
down vote
accepted
You need "dynamic SQL" because SQL will NOT allow you to use a parameter as a column name or a table name. You can only use parameters for data values such as in a where clause where column1 = @val
set @A = 'çolumn1'
Select @A from customerlist -- this fails because it is not allowed
Dynamic SQL is a "hack" to get around those restrictions as the SQL statement is placed into a string along with any value held by parameters.
set @A = 'çolumn1'
set @SQL = 'Select ' + @A + ' from customerlist;'
execute @SQL -- this works, the SQL statement is valid with no parameters as column names
The string formed as @SQL is a complete sql statement without needing any parameters as column names.
Note: the syntax I used here is incomplete and is based on MS SQL Server, different databases will use a different, but similar, syntax.
answered Nov 12 at 5:08
Used_By_Already
22.3k21838
add a comment |
up vote
1
down vote
accepted
You need "dynamic SQL" because SQL will NOT allow you to use a parameter as a column name or a table name. You can only use parameters for data values such as in a where clause where column1 = @val
set @A = 'çolumn1'
Select @A from customerlist -- this fails because it is not allowed
Dynamic SQL is a "hack" to get around those restrictions as the SQL statement is placed into a string along with any value held by parameters.
set @A = 'çolumn1'
set @SQL = 'Select ' + @A + ' from customerlist;'
execute @SQL -- this works, the SQL statement is valid with no parameters as column names
The string formed as @SQL is a complete sql statement without needing any parameters as column names.
Note: the syntax I used here is incomplete and is based on MS SQL Server, different databases will use a different, but similar, syntax.
answered Nov 12 at 5:08
Used_By_Already
22.3k21838
add a comment |
up vote
1
down vote
accepted
up vote
1
down vote
accepted
You need "dynamic SQL" because SQL will NOT allow you to use a parameter as a column name or a table name. You can only use parameters for data values such as in a where clause where column1 = @val
set @A = 'çolumn1'
Select @A from customerlist -- this fails because it is not allowed
Dynamic SQL is a "hack" to get around those restrictions as the SQL statement is placed into a string along with any value held by parameters.
set @A = 'çolumn1'
set @SQL = 'Select ' + @A + ' from customerlist;'
execute @SQL -- this works, the SQL statement is valid with no parameters as column names
The string formed as @SQL is a complete sql statement without needing any parameters as column names.
Note: the syntax I used here is incomplete and is based on MS SQL Server, different databases will use a different, but similar, syntax.
answered Nov 12 at 5:08
Used_By_Already
22.3k21838
You need "dynamic SQL" because SQL will NOT allow you to use a parameter as a column name or a table name. You can only use parameters for data values such as in a where clause where column1 = @val
set @A = 'çolumn1'
Select @A from customerlist -- this fails because it is not allowed
Dynamic SQL is a "hack" to get around those restrictions as the SQL statement is placed into a string along with any value held by parameters.
set @A = 'çolumn1'
set @SQL = 'Select ' + @A + ' from customerlist;'
execute @SQL -- this works, the SQL statement is valid with no parameters as column names
The string formed as @SQL is a complete sql statement without needing any parameters as column names.
Note: the syntax I used here is incomplete and is based on MS SQL Server, different databases will use a different, but similar, syntax.
answered Nov 12 at 5:08
Used_By_Already
22.3k21838
answered Nov 12 at 5:08
Used_By_Already
22.3k21838
answered Nov 12 at 5:08
Used_By_Already
22.3k21838
answered Nov 12 at 5:08
Used_By_Already
22.3k21838
22.3k21838
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add a comment |
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(1) You have a problem with your data model if you have columns that are really data fields. (2) This requires dynamic SQL, so you need to specify the database you are using.
– Gordon Linoff
Nov 12 at 2:00