Is it possible to select the first 20 columns from my table, without naming out each column in the select?
The columns are always ordered in the same way when I do a select, so there must be some underlying order.
The below query forms the SQL for you. It uses the dictionary table all_tab_columns to fetch the column names for the table.
SELECT ' SELECT '
|| REPLACE(LISTAGG(column_name,',') WITHIN GROUP( ORDER BY column_id),',',','
||CHR(10))
|| ' FROM YOUR_TABLE'
FROM all_tab_columns
WHERE owner ='YOUR_SCHEMA_NAME'
AND table_name='YOUR_TABLE_NAME'
AND column_id <= 20;
you can use column index instead of column name like select 0,1,2,.....
There is a table in a SQL Server database called sysColumns that records all the columns in every table. I think it is a SQL standard and should be in Oracle too.
EDIT: thanks to comment from #davegreen100, this table is in Oracle but is named DBA_TAB_COLUMNS.
try running Select * from DBA_TAB_COLUMNS and see what the results are, and work from there.
If it's there (in Oracle), you will eventually end up with something like
Select name from DBA_TAB_COLUMNS
Where id = #tableId -- <--- the id of the table
and colOrder <= 20
Your final SQL will be probably have to be generated dynamically using the output from the above
Related
I'd like to select a 2 column from lot of table.
Exemple
Table_2017-01
id name value
Table_2017-02
id name value
Table_2017-03
id name value
etc...
My Query would be
SELECT name, value
FROM Table_2017-01, Table_2017-02, Table_2017-03
But I'd like to know if something it's possible like
SELECT name, value FROM LIKE Table_%
I know this last query is not possible and it could be easier for me if a query exist for this problem as I can have a lot of table with just a part of the name different.
To select mutiple columns with the same name you have to the table as prefix like:
SELECT `Table_2017-01.name`, `Table_2017-02.name`, `Table_2017-03.name` FROM Table_2017-01,`Table_2017-02, Table_2017-03
If you want them in one Column, use Union.
(SELECT `Table_2017-01.name` from Table_2017-01)
Union
(SELECT `Table_2017-02.name` from Table_2017-02)
It depends on your database. Oracle f.e. has a data dictionary with all tables.
Because I know oracle better than others I use this for the example:
SELECT TABLE_NAME FROM ALL_TABLES WHERE TABLE_NAME LIKE 'Table_2017-%';
Now there are the following ways I sometimes use:
I build a list of selects and fire them into the database:
via Excel (not explained here)
via SQL
SELECT
'SELECT '''||TABLE_NAME||''' TABLE_NAME, NAME, VALUE FROM '||
TABLE_NAME
||' UNION '
FROM ALL_TABLES WHERE TABLE_NAME LIKE 'Table_2017-%';
Now you can copy the result to your database (dont forget to delete the last "UNION")
via program (python, Lazarus, c# .. whatever, same view is needed)
But pay attention: It is quick and dirty, the column names and types have to match.
select COLUMN_NAME
from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME='Submenu';
The above query gave all column names in Submenu table but I want only three column names of Submenu table.
Is there any way to get column names?
I assumed this is SQL Server, so the below queries might not work on other RDBMS's).
If your question is how to find only the column names you need (presuming you know in advance which ones those are), you would have to do something like this:
SELECT
COLUMN_NAME
FROM
INFORMATION_SCHEMA.COLUMNS
WHERE
TABLE_NAME='Submenu'
AND COLUMN_NAME IN ('Column1', 'Column2', 'Column3')
At this moment, you basically are requesting a list of any column within your table, without any restrictions whatsoever.
Alternatively, if you're looking only for the first three column names, this would work:
SELECT TOP 3
COLUMN_NAME
FROM
INFORMATION_SCHEMA.COLUMNS
WHERE
TABLE_NAME='Submenu'
ORDER BY
ORDERINAL_POSITION
In the latter case, you will have to determine how you want to sort the column names though (either by using something like ORDER BY COLUMN_NAME, in case you want them listed alphabetically, or ORDER BY ORDERINAL_POSITION in case you're trying to get them in the order they appear in the table).
If this is not what you meant, please elaborate on what you are trying to achieve.
SELECT TOP 3 COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'Submenu';
As easy as that!
How can I select the column name and table name from a SQL?
I tried something like this but it didn't work:
select column_name, table_name from (select * from users);
This might sound silly, but I have a list of different SQLs and I need to extract their columns and tables into a list. So some of the statements could me:
select username, password from users
select createdate from userlog
select * from dept
...
If I can select the column name and table name of a select statement, then I should get, say for the first statement, username and password for columns and users for table name. And createdate for column and userlog for table name in the second statement.
Then if it all works, I can then loop through the list of select statements and extract their column and table names.
The below query worked for Oracle database.
SELECT COLUMN_NAME,TABLE_NAME FROM ALL_TAB_COLUMNS
You can see more about information-schema
Edit:
You may try like this:
SELECT COLUMN_NAME,TABLE_NAME FROM ALL_TAB_COLUMNS
WHERE TABLE_NAME IN (SELECT ColumnName FROM users)
You need to parse the SQL statement so the SQL engine figures out the columns and datatypes of the columns that the statement returns.
How you do it best depends on what environment you are using. In some programming languages when you create a SqlPreparedStatement or OraCommand or whatever the object may be called, that object may have a metadata collection populated with column information after parsing.
If you are doing it in the database itself, parsing your statement with DBMS_SQL can get you the information you need. See Example 8 in the documentation at this link:
http://docs.oracle.com/database/121/ARPLS/d_sql.htm#ARPLS68205
--
Oh, and this gives you column names of the select statement. The table names I do not know of any way to get easily.
I want a query that returns me name of columns of a table.
I tried following query -
SELECT column_name ColName
FROM all_tab_columns
WHERE table_name ='<TABLENAME>';
but this query is returning duplicate column names.
I do not want to use distinct in my query cause it hampers the performance.
So is there a query which returns columns of a table without any duplicate.
This is the solution for getting column name from table.
select column_name,data_type from cols where Table_name='TEST_TABLE'
I'm am using MS Reporting Services to graph some data from an Oracle database. I want to name the columns in my select statement with values from another select statement. Is this possible?
Like instead of
Select Column1 As 'Test' From Table1
could I do something like
Select Column1 As (Select column2 from Table2 where Value = 1) From Table1
?
I would think you'd have to query out separately, then form the query dynamically. Interested to see if there is a different answer.
My PL/SQL's a little rusty, so what follows is more pseudocode than compilable & tested code. And this is completely off the top of my head. But if you know the specific ordinal location of the column in the table, you may try this:
columnName varchar2(50) :=
Select column_name
From all_tab_columns c
Where lower(table_name) = '<% Your Table2 Name %>' And
column_id = 9 -- The appropriate ordinal
Order By column_id;
Select Column1 As columnName From Table1;
There may be more column values drawn from "all_tab_columns" that'll help you as well. Take a look around and see.
I hope this helps.
You can query all needed column names into separate report dataset, create hidden multivalue report parameter vColumns, set dataset with columns as a parameter default values, and use it as a string array:
Parameters!vColumns(0).Value - will be the first column etc. So you can use them as a query parameters.
See Lesson 4: Adding a Multivalue Parameter