I'm using PL/pgSQL and I'm trying to append some rows to a table, or if the table doesn't exist yet I want to create it and append the rows.
Is there some built-in syntax for that?
You can use CREATE TABLE IF NOT EXISTS name (definition) before you INSERT data to it.
Related
I found the similar question and solution for the SQL server. I want to replace all my null values with zero or empty strings. I can not use the update statement because my table has 255 columns and using the update for all columns will consume lots of time.
Can anyone suggest to me, how to update all the null values from all columns at once in PostgreSQL?
If you want to replace the data on the fly while selecting the rows you need:
SELECT COALESCE(maybe_null_column, 0)
If you want the change to be saved on the table you need to use an UPDATE. If you have a lot of rows you can use a tool like pg-batch
You can also create a new table and then swap the old one and the new one:
# Create new table with updated values
CREATE TABLE new_table AS
SELECT COALESCE(maybe_null_column, 0), COALESCE(maybe_null_column2, '')
FROM my_table;
# Swap table
ALTER TABLE my_table RENAME TO obsolete_table;
ALTER TABLE new_table RENAME TO my_table;
How to create a table on the basis of result of select query in BigQuery?
For example:
create table abc as select x,y,z from mnp;
Is there any way or workaround to achieve the same in BigQuery?
Any leads?
Just try giving the GCP dataset name before table name in create table statement.
Example:
create table `GCP_Dataset.abc` as select x,y,z from mnp
CREATE OR REPLACE TABLE [GCP_Folder].abc AS SELECT x,y,z FROM mnp
This wont get the error Cannot set write disposition in jobs with DDL statements. no source to refer, its trial and error from my end.
already it can be done like
CREATE OR REPLACE TABLE project.dataset.table AS SELECT x,y,z FROM 'project.dataset.mnp'
You can create a table using another table as the starting point.
This method basically allows you to duplicate another table (or a part
of it, if you add a WHERE clause in the SELECT statement).
CREATE TABLE project_name.dataset_name.table (your destination) AS SELECT column_a,column_b,... FROM (UNION/JOIN for example)
Actually, I want to move one table to another database.
But spark don't permit this.
Then, how to copy table by spark-sql?
I already tried this.
SELECT *
INTO table1 IN new_database
FROM old_database.table1
But it was not working.
maybe try:
CREATE TABLE new_db.new_table AS
SELECT *
FROM old_db.old_table;
To preserve partitioning and storage format do the following-
Get the complete schema of the existing table by running-
show create table db.old_table
The above query will output the table schema which you can just execute after changing the path name and table name.
Then insert all the rows into the new blank table using-
insert into db.new_table select * from db.old_table
The following snippet will create a new table while preserving the definition of the "old" table.
CREATE TABLE db.new_table LIKE db.old_table;
For more info, check the doc's CREATE TABLE.
I want to create a table using CTAS of partitioned table.
New table must have all the data and partitions, subpartitions of old table.
How to do this?
You need to first create the new table with all the partitions, there is no way you can add partition definitions to a CTAS. Once the table is created you can populate it using insert into .. select.
You can use dbms_metadata.get_ddl to get the definition of the old table.
select dbms_metadata.get_ddl('TABLE', 'NAME_OF_EXISTING_TABLE')
from dual;
Save the output of that into a script, do a search and replace to adjust the table name, then run the create table and then run the insert into ... select ...
I need a query to create a table which is the exact replica but with different table name and without any data from the source table using a sql query!
You can try this
SELECT * INTO Table_Copy
FROM Table
where 1=2
It will create a empty table with the same structure.
SQL Server Management Studio
Object Explorer
Connect -> Your server
Databases -> Choose Database
Tables
Right Click Your Table
Script Table as -> Create To -> New Query Editor Window
Jonathan has it (upvoted), and you should probably go with that because it's more portable. I normally use something similar:
SELECT TOP 0 * INTO [New_Table] FROM [Old_Table]
I think this better expresses what you're doing, but I like Jonathan's because 'TOP 0' is SQL Server specific, and so his is more portable.
For MySQL, you can call SHOW CREATE TABLE table_name;
It will display a CREATE TABLE query. Simply change the table name in that query and you're good to go.
http://dev.mysql.com/doc/refman/5.1/en/show-create-table.html
If you use Postgresql:
CREATE TABLE LIKE table_name
http://www.postgresql.org/docs/8.1/static/sql-createtable.html
SELECT * INTO Table_Copy
FROM Table
where 1=2
This worked very well, when i tried to create a replica of the table without any data's.
SELECT * INTO Table_Copy
FROM Table
This will create a replica with the data's too.
This can help you:
CREATE TABLE foo AS SELECT...
Read more here
select * into newtablename from sourcetablename
go
truncate newtablename
go
That will result in an exact copy but it also copies the data at first which you remove with the truncate statement.
create table <new table name> as select * from <old tale name from which you would like to extract data>
It will create a new table with a different name but will copy all existing data from the old table to new table.
in postgres you can use INHERITS or LIKE keyword to make replica of a table(only copies structure of the table)
CREATE TABLE client_new (LIKE client);
or
CREATE TABLE client_new () INHERITS (client)
Use of INHERITS creates a persistent relationship between the new child table and its parent table(s). Schema modifications to the parent(s) normally propagate to children as well, and by default the data of the child table is included in scans of the parent(s).
LIKE clause specifies a table from which the new table automatically copies all column names, their data types, and their not-null constraints.Unlike INHERITS, the new table and original table are completely decoupled after creation is complete. Changes to the original table will not be applied to the new table, and it is not possible to include data of the new table in scans of the original table.