How do I drop a few tables (e.g. 1 - 3) using the output of a SELECT statement for the table names? This is probably standard SQL, but specifically I'm using Apache Impala SQL accessed via Apache Zeppelin.
So I have a table called tables_to_drop with a single column called "table_name". This will have one to a few entries in it, each with the name of another temporary table that was generated as the result of other processes. As part of my cleanup I need to drop these temporary tables whose names are listed in the "tables_to_drop" table.
Conceptually I was thinking of an SQL command like:
DROP TABLE (SELECT table_name FROM tables_to_drop);
or:
WITH subquery1 AS (SELECT table_name FROM tables_to_drop) DROP TABLE * FROM subquery1;
Neither of these work (syntax errors). Any ideas please?
even in standard sql this is not possible to do it the way you showed.
in standard sql usually you can use dynamic sql which impala doesn't support.
however you can write an impala script and run it in impala shell but it's going to be complicated for such task, I would prepare the drop statement using select and run it manually if this is one-time thing:
select concat('DROP TABLE IF EXISTS ',table_name) dropstatements
from tables_to_drop
Related
I do not fully understand the "USE" statement in Transact-SQL and how it affects the scope of temp tables. I have a user-defined table type in one database but not another, and I've found I need to "USE" that database in order to define a table of that type. Earlier in the query, I define a temporary table. After the "USE" statement, SSMS does not recognize the temp table as a valid object name, however I can still query from it without error.
The skeleton of my SQL query is as follows:
USE MYDATABASE1
[... a bunch of code I did not write...]
SELECT * INTO #TEMP_TABLE FROM #SOME_EARLIER_TEMP_TABLE
USE MYDATABASE2
DECLARE #MYTABLE MyUserDefinedTableType -- this table type only exists in MYDATABASE2
INSERT INTO #MYTABLE(Col1, Col2)
SELECT Col1, Col2 FROM (SELECT * FROM MYDATABASE2.dbo.SOME_TABLE_VALUED_FUNCTION(param1, param2)) T
SELECT A.*, B.Col2
FROM #TEMP_TABLE A
CROSS APPLY DATABASE2.dbo.SOME_OTHER_TABLE_VALUED_FUNCTION(#MYTABLE, A.SomeColumn) B
In the last SELECT statement, SSMS has red squiggly lines under "A.*" and "#TEMP_TABLE", however there is no error running the query.
So my question is: am I doing something "wrong" even though my query still works? Assuming the initial "USE MYDATABASE1" is necessary, what is the correct way to switch databases while still having #TEMP_TABLE available as a valid object name? (Note that moving the definition of #TEMP_TABLE to after "USE MYDATABASE2" would just shift the problem to #SOME_EARLIER_TEMP_TABLE.)
In SQL USE basically tells the query which database is the "default" database.
Temp tables can play tricks on intellisense - unless they're explicitly defined using the CREATE TABLE #MyTempTable route, intellisense doesn't really know what to do with them a lot of the time. Don't worry though - temp tables are scoped to the query.
Although I do feel it's worth pointing out: while UDTs are database specific, you can create an assembly to use across databases
I need to copy tables from a linked server onto my local machine. I am working in SQL management studio. The linked server is Oracle based. My end goal is to set up a stored proc that deletes a table if it exists and creates a new table in its place with refreshed data. This will be done for many tables as needed. The issue with the below code is that I get the error:
Incorrect syntax near the keyword 'SELECT'.
I am stuck at creating the table.
CREATE TABLE test AS
SELECT DUMMY
FROM OPENQUERY (LServer, '
Select *
from sourceT
');
The data in the dummy table is just one column with a single value "x". I have seen posts that suggest using a certain notation in naming the linked server table, like <server.database.schema.tablename> but this doesn't seem to work,even if I just run the select statement using the openquery. If I just run the select part in the script above, this does work.
CREATE TABLE test AS
Is valid in Oracle but not SQL Server
You want
-- if the table already exists drop it
DROP TABLE IF EXISTS test;
-- now create a table and load into it
SELECT DUMMY
INTO test
FROM OPENQUERY (LServer, '
Select *
from sourceT')
We have a table on the SQL Server 2008 which gets populated by various stored procedures. The problem is that the authors of these stored procedures used some poor choice in code and populated this table using the following syntax:
INSERT INTO persistant_table
SELECT *
FROM #temp_table_with_data
Basically they would create a #temp_table_with_data in the script and the columns would be in the same order and with the same name as they are in the persistant_table.
Now I need to add another column to this persistant_table, but if I do that, I will break all the stored procedures.
Is there a way for me to add a column to this table without breaking all the stored procedures? (In the long run, we will change the stored procedures).
Thank you
No I think.select * will pick all columns and column number should match.
I don't think it's big effort to change the line to have particular columns only or select statement to have default value for column or null and then * to store into columns sequentially. But at least 1 line to be changed
The "ALTER TABLE" is a SQL statement that allows you to make datatype changes to a database table (i.e. change datatype as well as Size columns from an existing table).
ALTER TABLE TableName ALTER COLUMN ColumnName NVARCHAR(200)
You cannot do it without affecting old scripts. This is why 'SELECT *' is not good practice. You'd better create new scripts with explicit column names like
SELECT column1, column2 ....
I Know of this below mentioned command for copying table fully but i am not able to figure out how this command will work because i cant just find the mentioning of newly created table. (courtesy SO).
SET LONG 5000
SELECT dbms_metadata.get_ddl( 'TABLE', 'MY_OLD_TABLE_NAME' ) FROM DUAL;
And also i read in some oracle forum posts that this is not a one shot solution to copy table ,its data and all the constraints , triggers , indexes and other such objects.
IS this true ?
Simplest way to export is use pl/sql developer or sql developer and use export data functionality. They export entire table with constraints, indexes, data. Just give it a try.
I am not sure what you meant by "copy a table including DDL statements". If you are looking to create a new table using dbms_metadata.get_ddl, then the above command will actually need to be modified as (not tested) :-
Assuming that variable tbl_sql has been defined in plsql block having length of 32767, you can do :-
SELECT REPLACE(DBMS_LOB.SUBSTR(dbms_metadata.get_ddl('TABLE','MY_OLD_TABLE_NAME'),32760,1),'MY_OLD_TABLE_NAME','NEW_TABLE_NAME') INTO tbl_sql FROM DUAL;
EXECUTE IMMEDIATE tbl_sql;
If you want to create a new table, then the following might be even better :-
EXECUTE IMMEDIATE 'CREATE TABLE NEW_TABLE_NAME AS SELECT * FROM MY_OLD_TABLE_NAME';
The dbms_metadata.get_ddl statement will not copy your data. However, the second statement (CTAS) will copy your data also.
Both the statements do not copy the constraints (CTAS does copy NOT NULL constraints) and indexes (as far as I know). To copy indexes, you will have to execute the dbms_metadata.get_ddl statement passing 'INDEX' as the first argument.
SELECT REPLACE(DBMS_LOB.SUBSTR(dbms_metadata.get_ddl('INDEX','MY_OLD_INDEX_NAME'),32760,1),'MY_OLD_INDEX_NAME','NEW_INDEX_NAME') INTO idx_sql FROM DUAL;
EXECUTE IMMEDIATE idx_sql;
keep it simple
create table xyz_new as select * from xyz where 1=0;
Create table with indexes ( More useful )
create table xyz_new like xyz
I am trying to write an SQL query which needs to be compatible on both a Sybase and Oracle database. The query looks like the following :
SELECT *
INTO new_table
FROM other_table
This query is working great on a Sybase database but not on an Oracle one. I found the equivalent for Oracle :
CREATE table new_table AS
SELECT *
FROM other_table
Is there a way to write a third query that would do the same and that can be executed on a Sybase and on an Oracle database?
As you found, Oracle supports INTO but doesn't use it like Sybase/SQL Server do. Likewise, Sybase doesn't support Oracle's extension of the CREATE TABLE syntax.
The most reliable means of creating a table & importing data between the systems is to use two statements:
CREATE TABLE new_table (
...columns...
)
INSERT INTO new_table
SELECT *
FROM OLD_TABLE
Even then, syntax is different because Oracle requires each statement to be delimited by a semi-colon when TSQL doesn't.
Creating a table & importing all the data from another table is a red flag to me - This is not something you'd do in a stored procedure for a production system. TSQL and PLSQL are very different, so I'd expect separate scripts for DML changes.
There is no query that would do what you want. These environments are very different.
It is possible.
SELECT * INTO new_table FROM existing_table;
Thanks