I have to change a procedure in such a way to make it dependable on user ID. The procedure includes several SELECT INTO statements and SELECT statement at the end, which returns data.
I wanted to add IF condition which will check user ID and execute SELECT INTO statement for this condition. However the problem is that there can't be the same tables in two conditions.
One can't execute this code:
select '1' as Number into ##temp
if 1=1
begin
select * into ##temp2 from ##temp
end
else
begin
select * into ##temp2 from ##temp
end
Could you just create the structure of the second table first, then insert into it accordingly?
select '1' as Number into ##temp
select * into ##temp2 from ##temp where 1=0
if 1=1
begin
insert into ##temp2 select * from ##temp
end
else
begin
insert into ##temp2 select * from ##temp
end
Related
imagine there are 5 schemas in my database and in every schema there is a common name table (ex:- table1) after every 5mins records get inserted in table1, how I can iterate in all schemas n calculate the count of table1[i have to automate the process so i am going to write the code in function and call that function after every 5mins using crontab].
Basically 2 options: Hard code schema.table and union the results. So something like:
create or replace function count_rows_in_each_table1()
returns table (schema_name text, number_or_rows integer)
language sql
as $$
select 'schema1', count(*) from schema1.table1 union all
select 'schema2', count(*) from schema2.table1 union all
select 'schema3', count(*) from schema3.table1 union all
...
select 'scheman', count(*) from scheman.table1;
$$;
The alternative being building the query dynamically from information_scheme.
create or replace function count_rows_in_each_table1()
returns table (schema_name text, number_of_rows bigint)
language plpgsql
as $$
declare
c_rows_count cursor is
select table_schema::text
from information_schema.tables
where table_name = 'table1';
l_tbl record;
l_sql_statement text = '';
l_connector text = '';
l_base_select text = 'select ''%s'', count(*) from %I.table1';
begin
for l_tbl in c_rows_count
loop
l_sql_statement = l_sql_statement ||
l_connector ||
format (l_base_select, l_tbl.table_schema, l_tbl.table_schema);
l_connector = ' union all ';
end loop;
raise notice E'Running Query: \n%', l_sql_statement;
return query execute l_sql_statement;
end;
$$;
Which is better. With few schema and few schema add/drop, opt for the first. It is direct and easily shows what you are doing. If you add/drop schema often then opt for the second. If you have many schema, but seldom add/drop them then modify the second to generate the first, save and schedule execution of the generated query.
NOTE: Not tested
I am using psql (PostgreSQL) 11.2 (Debian 11.2-1.pgdg90+1).
I am trying to write a logic in .PSQL file that needs to import some data into a table if this table is empty, else do something else.
I am struggling to find the correct syntax to make it work.
Would appreciate some help around this.
DO $$ BEGIN
SELECT count(*) from (SELECT 1 table_x LIMIT 1) as isTableEmpty
IF isTableEmpty > 0
THEN
INSERT INTO table_x
SELECT * FROM table_b;
ELSE
INSERT INTO table_y
SELECT * FROM table_b;
END IF;
END $$;
thanks!
Read plpgsql structure. Then you would know you need a DECLARE section to declare isTableEmpty and from here Select into that you need to select into the isTableEmpty variable. So:
...
DECLARE
isTableEmpty integer;
BEGIN
SELECT count(*) into isTableEmpty from (SELECT 1 table_x LIMIT 1);
...
Though I'm not sure what you are trying to accomplish with?:
SELECT count(*) from (SELECT 1 table_x LIMIT 1) as isTableEmpty
As that is always going to return 1.
You are using count just to determine that a row exists or not in the table. To do so you need to create a variable in the DO block, select into that variable, and reference that variable. This is all unnecessary; you can just use exists(...) instead of count(*) .... See demo;
do $$
begin
if not exists (select null from table_x) then
insert into table_x (...)
values (...);
else
insert into table_y (...)
values (...);
end if;
end ;
$$;
I was attempting an INSERT INTO.... ( SELECT... ) (inserting a batch of rows from SELECT... subquery), onto the same table in my database. For the most part it was working, however, I did see a "Deadlock" exception logged every now and then. Does it make sense to do this or is there a way to avoid a deadlock scenario? On a high-level, my queries both resemble this structure:
CREATE OR REPLACE PROCEDURE myConcurrentProc() LANGUAGE plpgsql
AS $procedure$
DECLARE
BEGIN
LOOP
EXIT WHEN row_count = 0
WITH cte AS (SELECT *
FROM TableA tbla
WHERE EXISTS (SELECT 1 FROM TableB tblb WHERE tblb.id = tbla.id)
INSERT INTO concurrent_table (SELECT id FROM cte);
COMMIT;
UPDATE log_tbl
SET status = 'FINISHED',
WHERE job_name = 'tblA_and_B_job';
END LOOP;
END
$procedure$;
And the other script that runs in parallel and INSERTS... also to the same table is also basically:
CREATE OR REPLACE PROCEDURE myConcurrentProc() LANGUAGE plpgsql
AS $procedure$
DECLARE
BEGIN
LOOP
EXIT WHEN row_count = 0
WITH cte AS (SELECT *
FROM TableC c
WHERE EXISTS (SELECT 1 FROM TableD d WHERE d.id = tblc.id)
INSERT INTO concurrent_table (SELECT id FROM cte);
COMMIT;
UPDATE log_tbl
SET status = 'FINISHED',
WHERE job_name = 'tbl_C_and_D_job';
END LOOP;
END
$procedure$;
So you can see I'm querying two different tables in each script, however inserting into the same some_table. I also have the UPDATE... statement that writes to a log table so I suppose that could also cause issues. Is there any way to use BEGIN... END here and COMMIT to avoid any deadlock/concurrency issues or should I just create a 2nd table to hold the "tbl_C_and_D_job" data?
I want to select a column from a table, with the column name being the result of a query like the following:
-- This query returns a single value
with x as (
select a from table1 where <condition>
)
-- my_function() yields a table
select x from my_function()
How do I do that?
Thank you very much.
You could write it in SQL with a temporary function:
CREATE FUNCTION pg_temp.tablefunc()
RETURNS SETOF my_function_result_type
LANGUAGE plpgsql AS
$$DECLARE
v_colname text;
BEGIN
SELECT a INTO v_colname
FROM table1
LIMIT 1;
RETURN QUERY EXECUTE
format(E'SELECT %I\n'
'FROM my_function()',
v_colname);
END;$$;
SELECT * FROM pg_temp.tablefunc();
I have 3 queries. If the first one returns empty set, I execute the second query, and if it returns empty set too, I give to the server the last chance and do the third:
SELECT ... INTO #Query1
IF EXISTS(SELECT * FROM #Query1)
SELECT * FROM #Query1
ELSE BEGIN
SELECT ... INTO #Query2
IF EXISTS(SELECT * FROM #Query2)
SELECT * FROM #Query2
ELSE BEGIN
SELECT ...
END
END
It worked well, but I've faced a new task - the query should be used as a subquery as well as other queries, within IF EXISTS([subquery]). Doing this, I see
Incorrect syntax near the keyword 'INTO'.
How should I modify the original query to meet this new condition?
Regards,
Are you looking for something like this:
create function dbo.Foo()
returns #Result table ( ThingId Int, Source Int )
as
begin
insert into #Result
select ThingId, 1 as Source from Things1
if ##ROWCOUNT = 0
insert into #Result
select ThingId, 2 as Source from Things2
if ##ROWCOUNT = 0
insert into #Result
select ThingId, 3 as Source from Things3
--...
return
end
go
select * from dbo.Foo()
select 42 as 'The Answer' where exists ( select * from dbo.Foo() where Source > 9 )
You can pass parameters into the function to use in WHERE clauses and the like. The Source column may be omitted if you don't care to know where the data originated.