I have to back up a table, which can change number of column. When my etl script starts it doesn't know the number of column. How can I create INSERT INTO table VALUES (?1, ?2, ...) script on the fly?
Regards,
Jacek
Depending on the database, one can use CREATE TABLE FROM SELECT (or similar) to back up the table. Example:
CREATE TABLE new_table AS (SELECT * FROM old_table);
Related
I have a Snowflake stored procedure and I want to use "insert into" without hard coding column names.
INSERT INTO MEMBERS_TARGET (ID, NAME)
SELECT ID, NAME
FROM MEMBERS_STREAM;
This is what I have and column names are hardcoded. The query should copy data from MEMBERS_STREAM to MEMBERS_TARGET. The stream has more columns such as
METADATA$ACTION | METADATA$ISUPDATE | METADATA$ROW_ID
which I am not intending to copy.
I don't know of a way to not copy the METADATA columns if not hardcoding. However if you don't want the data maybe the easiest thing to do is to add them to your target, INSERT using a SELECT * and later in the sp set them to NULL.
Alternatively, earlier in your sp, run an ALTER TABLE ADD COLUMN to add the columns, INSERT using SELECT * and then after that run an ALTER TABLE DROP COLUMN to remove the columns? That way your table structure stays the same, albeit briefly it will have some extra columns.
A SELECT * is not usually recommended but it's the easiest alternative I can think of
I have downloaded sqlite manager app in Firefox browser and open sqlite manager app.
1) Created database named DBSQLTEST.
2) Created table named SQLTEST contain has threes fields are SLNO, NAME and AGE
3) Inserted new records
But i want remove a ‘AGE’ column in sqltest table
i using sql command like below
ALTER TABLE SQLTEST DROP COLUMN AGE
SQLiteManager message says
SQLiteManager: Likely SQL syntax error: ALTER TABLE SQLTEST DROP COLUMN AGE [ near "DROP": syntax error ]
Exception Name: NS_ERROR_FAILURE
Exception Message: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [mozIStorageConnection.createStatement]
What is error that?
sqlite does not support DROP COLUMN in ALTER TABLE. You can only rename tables and add columns.
Reference: http://www.sqlite.org/lang_altertable.html
If you need to remove columns, create a new table, copy the data there, drop the old table and rename the table to its intented name.
SQLite does not fully support ALTER TABLE statements. You can only rename table, or add columns.
If you want to drop a column, your best option is to create a new table without the column, and to drop the old table in order to rename the new one.
For example, suppose you have a table named "t1" with columns names "a", "b", and "c" and that you want to delete column "c" from this table. The following steps illustrate how this could be done:
BEGIN TRANSACTION;
CREATE TEMPORARY TABLE t1_backup(a,b);
INSERT INTO t1_backup SELECT a,b FROM t1;
DROP TABLE t1;
CREATE TABLE t1(a,b);
INSERT INTO t1 SELECT a,b FROM t1_backup;
DROP TABLE t1_backup;
COMMIT;
Credits to Benoit.
Create a table
CREATE TABLE SQLTEST ("SLNO" INTEGER PRIMARY KEY ,"NAME" TEXT,AGE INTEGER)
If want to remove a column
ALTER TABLE SQLTEST RENAME TO SQLTESTCOPY
CREATE TABLE SQLTEST ("SLNO" INTEGER PRIMARY KEY ,"NAME" TEXT)
INSERT INTO SQLTEST"SELECT "SLNO","NAME" FROM SQLTESTCOPY
DROP TABLE SQLTESTCOPY
easy.
I'm searching a way to simulate "create table as select" in Firebird from SP.
We are using this statement frequently in another product, because it is very easy for make lesser, indexable sets, and provide very fast results in server side.
create temp table a select * from xxx where ...
create indexes on a ...
create temp table b select * from xxx where ...
create indexes on b ...
select * from a
union
select * from b
Or to avoid the three or more levels in subqueries.
select *
from a where id in (select id
from b
where ... and id in (select id from c where))
The "create table as select" is very good cos it's provide correct field types and names so I don't need to predefine them.
I can simulate "create table as" in Firebird with Delphi as:
Make select with no rows, get the table field types, convert them to create table SQL, run it, and make "insert into temp table " + selectsql with rows (without order by).
It's ok.
But can I create same thing in a common stored procedure which gets a select sql, and creates a new temp table with the result?
So: can I get query result's field types to I can create field creator SQL from them?
I'm just asking if is there a way or not (then I MUST specify the columns).
Executing DDL inside stored procedure is not supported by Firebird. You could do it using EXECUTE STATEMENT but it is not recommended (see the warning in the end of "No data returned" topic).
One way to do have your "temporary sets" would be to use (transaction-level) Global Temporary Table. Create the GTT as part of the database, with correct datatypes but without constraints (those would probably get into way when you fill only some columns, not all) - then each transaction only sees it's own version of the table and data...
Sybase Advantage Database
I am doing a query
INSERT INTO nametable
SELECT * FROM nametable WHERE [indexkey]=32;
UPDATE nametable Set FieldName=1
WHERE [IndexKey]=(SELECT max([indexKey]) FROM nametable);
The purpose is to copy a given record into a new record, and then update the newly created record with some new values. The "indexKey" is declared as autoinc and is the primary key to the table.
I am not sure if this can be achieved in a single statement with better speed or;;; suggestions appreciated.
It can be achieved with a single statement but it will make the code more susceptible to schema changes. Suppose that there are 2 additional columns in the table besides the FieldName and the indexKey columns. Then the following statement will achieve your objective.
INSERT INTO nametable ( FieldName, Column2, Column3 )
SELECT 1, Column2, Column3 FROM nametable WHERE [indexkey]=32
However, if the table structure changes, this statement will need to be updated accordingly.
BTW, your original implementation is not safe in multi-user scenarios. The max( [indexKey] ) in the UPDATE statement may not be the one generated by the INSERT statement. Another user could have inserted another row between the two statements. To use your original approach, you should use the LastAutoInc() scalar.
UPDATE nametable Set FieldName=1
WHERE [IndexKey] = LastAutoInc( STATEMENT )
I'm writing a migration to convert a non-rails app into the right format for rails - one of the tables for some reason does not have auto increment set on the id column. Is there a quick way to turn it on while in a migration, maybe with change_column or something?
You need to execute an SQL statement.
statement = "ALTER TABLE `users` CHANGE `id` `id` SMALLINT( 5 ) UNSIGNED NOT NULL AUTO_INCREMENT"
ActiveRecord::Base.connection.execute(statement)
Note this is just an example. The final SQL statement syntax depends on the database.
If you're on postgesql, a single request won't make it. You'll need to create a new sequence in the database.
create sequence users_id_seq;
Then add the id column to your table
alter table users
add id INT UNIQUE;
Then set the default value for the id
alter table users
alter column id
set default nextval('users_id_seq');
Then populate the id column. This may be quite long if the table has many rows
update users
set id = nextval('users_id_seq');
Hope this helps postgresql users...
The Postgres answer by #jlfenaux misses out on the serial type, which does all of it for you automatically:
ALTER TABLE tbl add tbl_id serial;
More details in this related answer.