I want to select all rows from two tables that have the same number of columns where the columns have the same name and type.
e.g. table 2 is basically a continuation of table 1 and so I want any queries to look through both tables to find the best match.
How would I do that since SELECT would normally just add the second table's columns to the first table.
Yes, there is. For SELECT only you could use compound query:
SELECT *
FROM tab1
UNION ALL
SELEECT *
FROM tab2;
or create view:
CREATE VIEW my_view
AS
SELECT *
FROM tab1
UNION ALL
SELECT *
FROM tab2;
SELECT * FROM my_view;
Related
I have 10 tables having same columns.I made separate data for year wise like 2011,2012 .. 2020.
I made one view for combine all the tables data using union all.
create view as a combine
select * from table_2011
union all
select * from table_2012
..
union all
select * from table_2020;
Now when I run some query which having group by its taking 9 Minutes to return data.
select name, count(name) from combine group by name;
Can any one help me how to improve speed of view? I already give index to all the tables and columns.
Add Index to name column on your view
I need a way to get a "description" of the columns from a SELECT query (cursor), such as their names, data types, precision, scale, etc., in PostgreSQL (or better yet PL/pgSQL).
I'm transitioning from Oracle PL/SQL, where I can get such description using a built-in procedure dbms_sql.describe_columns. It returns an array of records, one for each column of a given (parsed) cursor.
EDB has it implemented too (https://www.enterprisedb.com/docs/en/9.0/oracompat/Postgres_Plus_Advanced_Server_Oracle_Compatibility_Guide-127.htm#P13324_681237)
An examples of such query:
select col1 from tab where col2 = :a
I need an API (or a workaround) that could be called like this (hopefully):
select query_column_description('select col1 from tab where col2 = :a');
that will return something similar to:
{{"col1","numeric"}}
Why? We build views where these queries become individual columns. For example, view's query would look like the following:
select (select col1 from tab where col2 = t.colA) as col1::numeric
from tab_main t
http://sqlfiddle.com/#!17/21c7a/2
You can use systems table :
First step create a temporary view with your query (without clause where)
create or replace view temporary view a_view as
select col1 from tab
then select
select
row_to_json(t.*)
from (
select
column_name,
data_type
from
information_schema.columns
where
table_schema = 'public' and
table_name = 'a_view'
) as t
I would like to create a new table as the result of the union of two tables without duplicates. I searched in stackoverflow and I found a question with exactly what I want but using mysql Create a new table from merging two tables with union.
Solution in mysql
CREATE TABLE new_table
SELECT * FROM table1
UNION
SELECT * FROM table2;
I tried to do something similar but I got:
SQL error.
I would like to achieve this if is possible with an statement similar to mysql.
I know that if you create a new table first with the fields that I want. I can do a select into this table over the union of this tables. If there aren't other option well I have to do something like this.
But in summary If possible to do something similar to the question with mysql in postgres. I would like to use syntactic sugar to do that
Thanks in advance
Update
In order to clarify I have two table with equal structure
TABLE1(id,field1,field2,field3)
TABLE2(id,field1,field2,field3)
and The table that I want
TABLE3(id,field1,field2,field3)
Notice that I tried
CREATE TABLE new_table as
SELECT * FROM table1
UNION
SELECT * FROM table2;
and it works but didn't put the fields in the correct place for example put field3 of table 1 in field 1 of table_result
You are missing the AS keyword:
CREATE TABLE new_table
AS
SELECT * FROM table1
UNION
SELECT * FROM table2;
If you need the columns in a specific order, then specify them in the select:
CREATE TABLE new_table
AS
SELECT id, column1, column2, column3
FROM table1
UNION
SELECT id, column1, column2, column3
FROM table2;
More details in the manual:
https://www.postgresql.org/docs/current/static/sql-createtableas.html
I have a view and two tables. Tables one and two have the same columns, but table one is has as small number of records, and table two has old data and a huge number of records.
I have to join a view with these two tables to get the latest data from table one; if a record from the view is not available in table one then I have to select the record from table two.
How can i achieve this with MySQL?
I came to know by doing some research in internet that we can't apply full join and sub query in from clause.
Just do a simple UNION of the results excluding the records in table2 that are already mentioned in table1:
SELECT * FROM table1
UNION
SELECT * FROM table2
WHERE NOT EXISTS (SELECT * FROM table1 WHERE table2.id = table1.id)
Something like this.
SELECT *
FROM view1 V
INNER JOIN (SELECT COALESCE(a.commoncol, b.commoncol) AS commoncol
FROM table1 A
FULL OUTER JOIN table2 B
ON A.commoncol = B.commoncol) C
ON v.viewcol = c.commoncol
If you are using Mysql then check here to simulate Full Outer Join in MySQL
are you trying to update the view from two tables where old record in view needs to be overwritten by latest/updated record from table1 and non existant records from table1 to be appended from table2?
, or are you creating a view from two tables?
I want to create a new table called table2 from another table called table1 without importing data and constraints. I used this query:
create table2 as select * from table1 where 1=2;
this code created table2 without any data, but imports constraints from table1. Is there a way not to import constraints from table1?
The answer can be found in the question create table with select union has no constraints.
If the select is a union, Oracle will not add any constraints, so simply use the same select twice, and be sure not to include any records in the second select:
create table2 as
select * from table1 where 1=2
union all
select * from table1 where 1=2;