SQL query over multiple tables in one database - sql

Question

enter code hereI have the following problem:
I have a bunch of Tables in a Vertica Database say:
+------------+
| Tablenames |
+------------+
| a_1 |
| a_2 |
| a_34 |
| b_1 |
| b_4 |
+------------+
The tables are not exactly the same but have mostly similar entries. And now I want to make one query over all tables that start with a_ (a_1 a_2 a_34).
Is there a way to search through all the tables for the string a_ in their name, output some sort of list and than either use a for loop or join operation with the generated list?
Once I get the new table (lets call it temp_table) that has all the table names that start with a_ I would like to run one query over all of them, something like that (Matlab syntax):
for ii=1:length(temp_table)
Data{ii}=SELECT * FROM temp_table(ii) WHERE paste_condition_here
end
So Data should be a new table that appends the new rows with each iteration.

Answer 1

#Nirjihar - there is on information_schema (you need v_catalog), you are confusing with MySQL.
select TABLE_NAME from v_catalog.TABLES where TABLE_NAME like 'a_%';
This will return all tables with a criteria of 'a_%'
Just as a complement !
In Vertica you won`t have loops ! For this you have to use UDP(user defined procedures), this can be written in the language of your choice (shell,java,R,C++).
i will go ahead and post on model here for you :
1 - Shell proc - to be created in the procedures folder
#!/bin/bash
. /home/dbadmin/.profile
/opt/vertica/bin/vsql -U $username -w $password -t -o /tmp/query.sql -c"
SELECT
' select * from '
||TABLE_SCHEMA
||'.'
||TABLE_NAME
||';'
FROM
v_catalog.TABLES where TABLE_NAME like '%$1%'
"
/opt/vertica/bin/vsql -U $username -w $password -F $'|' -At -o /tmp/query_output.csv -f /tmp/query.sql
2 - change sh file privs
chmod 4750 query_table.sh
3 - make sure you have the .profile file populated accordingly
. /home/dbadmin/.profile
#!/bin/bash
username=dbadmin
password=secrectpasswd
export username
export password
Note: this is to avoid passwd in text and only have one point of text passwd
4 - Register the UDP with Vertica Catalog
. /home/dbadmin/.profile
admintools -t install_procedure -f /vertica/catalog//procedures/query_table.sh -d -p $password
5 -Create the UDP inside the database
. /home/dbadmin/.profile
/opt/vertica/bin/vsql -U $username -w $password -c "CREATE PROCEDURE dba.query_table(table_name varchar) AS 'query_table.sh' LANGUAGE 'external' USER 'dbadmin';"
6 - execute the proc
select dba.query_table('you possible table name here');
7 - check results
a - you will get a file with the query
b - one file with the exported data(csv '|' delimited).
i have a similar post here:
http://www.aodba.com/create-vertica-schema-fly/

Answer 2

To get all the tables that start from a_:-
select TABLE_NAME from INFORMATION_SCHEMA.TABLES where TABLE_NAME like 'a_%'
Then you can alias this and join the list or each table as you like.