I need to update a column in all rows in my table. I have a query which can do it for one row, but how to update all rows iterating each row at a time with a function?
I've tried something like this, but the syntax seems not to be correct.
CREATE OR REPLACE FUNCTION update_file_name()
$BODY$
BEGIN
UPDATE myTable
SET file = REPLACE(file, file, CONCAT(file, 'addingStringToTheEnd'))
END;
$BODY$
LANGUAGE 'plpgsql' VOLATILE;
alter function update_file_name()
Basically I expect to iterate every row and update the value of this column "file" editing the string, but I could not find a simple example which does that.
As mentioned in the comments, to update all rows in a table you shouldn't use a WHERE clause.
Here is a simple example that replaces all 'o' occurrences to 'a' in the column text of the table t1.
CREATE OR REPLACE FUNCTION public.update_o()
RETURNS void
LANGUAGE plpgsql
VOLATILE
AS $BODY$
BEGIN
UPDATE public.t1 SET text = REPLACE(text, 'o', 'a');
END;
$BODY$;
To invoke this function use:
SELECT update_o();
Related
I have a really simple problem and I am probably overthinking this way too much. But here it goes:
I want the fields of a column in one of my tables to be filled automatically whenever I make a new record. The value should be the same (UUID) as the specified (UUID) value from a column in another table. These two columns are joined via a foreign key. So far I have tried making a trigger function but with no results so far:
Create or replace function project_id()
returns trigger
as $$ begin
if new.project_id is null then
insert into sporen (project_id)
select project_id
from project_info
where project_code = 'ant0001';
end if;
return new;
end;
$$ language plpgsql;
CREATE TRIGGER
project_id_default
BEFORE update ON
sporen
FOR EACH ROW EXECUTE PROCEDURE project_id();
Do I need to specify something as a default in my table? Or am I going about it completely wrong?
You only need to assign project_info.project_id to NEW.project_id in your trigger function. No INSERT is needed. Here is an illustration.
Create or replace function project_id() returns trigger as
$$
begin
if new.project_id is null then
new.project_id :=
(
select pi.project_id
from project_info pi
where pi.project_code = NEW.project_code
);
end if;
return new;
end;
$$ language plpgsql;
You do not need to specify a default value for project_id in your table.
I try to automatize some calculations on tables in my database. I try to perform some UPDATE on rows that are newly inserted in a table, but I newer used NEW or OLD statements before. I tried writing the code that updates happen on new values by assigning NEW.[tablename], but it wont work. Isn't there any statement in the beginning of the trigger function to specify running the function only on new values, I cannot find useful information about this.
CREATE OR REPLACE FUNCTION cost_estimation()
RETURNS TRIGGER AS
$func$
DECLARE
a INTEGER := 3;
BEGIN
UPDATE NEW.cost_table
SET column4 = a;
UPDATE NEW.cost_table
SET column 5 = column4 - column2;
[...]
RETURN NEW;
END
$func$ language plpgsql
UPDATE:
Thank you for the answers so far.
My original code is written based on the update structure, and needs to be rewritten when omitting UPDATE. I should give a better example of my situation. Easy spoken: I have a table (T1) which will be filled with data from another table (T2).
After data is inserted in T1 from T2 I want to run calculations on the new values inside of T1.(The code includes PostGIS functionalities):
CREATE OR REPLACE FUNCTION cost_estimation()
RETURNS TRIGGER AS
$func$
BEGIN
NEW.column6 = column2 FROM external_table WHERE
St_Intersects(NEW.geom, external_table.geom) LIMIT1;
NEW.column8 = CASE
WHEN st_intersects(NEW.geom, external_table2.geom) then 'intersects'
WHEN (NEW.column9 = 'K' and NEW.column10 <= 6) then 'somethingelse'
ELSE 'nothing'
END
FROM external_table2;
[...]
RETURN NEW;
END
$func$ language plpgsql
CREATE TRIGGER table_calculation_on_new
BEFORE INSERT OR UPDATE ON cost_estimation
FOR EACH ROW EXECUTE PROCEDURE road_coast_estimation();
After inserting values in my table no calculations will be performed.
UPDATE2: I checked my tables again and detected that another trigger was blocking the table operation. The code in the lower half is working fine now, thanks to #a_horse_with_no_name.
NEW and OLD aren't "statements", those are records that represent the modified rows from the DML statement that fired the trigger.
Assuming the trigger is defined on cost_table you can simply change the fields in the NEW record. No need to UPDATE anything:
CREATE OR REPLACE FUNCTION cost_estimation()
RETURNS TRIGGER AS
$func$
DECLARE
a INTEGER := 3;
BEGIN
new.column4 := a;
new.column5 := new.column4 - new.column2;
return new;
END;
$func$ language plpgsql
For this to work the trigger needs to be defined as a BEFORE trigger:
create trigger cost_table_trigger
BEFORE insert or update on cost_table
for each row execute procedure cost_estimation();
I'm trying to update a field in a temporary table I've created.
The code for the temporary table looks like this:
CREATE OR REPLACE FUNCTION insertTable ()
RETURNS VOID AS $$
BEGIN
execute 'create temporary table myTable (id INTEGER, value TEXT) on commit preserve rows';
execute 'insert into myTable values(1, NULL)';
end if;
end;
$$ LANGUAGE plpgsql;
Next I try to update the value filed with the following function:
CREATE OR REPLACE FUNCTION setValue (msg TEXT)
RETURNS VOID AS $$
BEGIN
EXECUTE format('UPDATE myTable SET value = value || $1 WHERE id = '|| quote_literal(1))USING msg;
END;
$$ LANGUAGE plpgsql;
However it does not work and the value field stays empty.
I tried the same code with an already existing table (not temporary) and the code worked as expected.
I searched the documentation for a difference between updating a temporary and a normal table but couldn't find any.
I hope you can help me with this.
Thanks in advance for your help.
Edit: edited the name of the table
The issue is not related to temporary table. The problem is that the column you want to update is actually empty. You try to update this column by concatenating the value of the column with another text, but, because the value itself is null, the concatenated value is also null.
This query:
SELECT null||'some text';
returns null. Also this update statement:
UPDATE xmlBuffer SET value = value || 'some text';
will not update the rows where the actual content is null. You could fix this issue in several ways, depending on you needs. In example you could use the COALESCE statement in the second function, using a empty string as fallback value (besides, the quote_literal and formatstatements are not necessary):
CREATE OR REPLACE FUNCTION setValue (msg TEXT)
RETURNS VOID AS $$
BEGIN
EXECUTE 'UPDATE xmlBuffer SET value = COALESCE(value,'''') || $1 WHERE id = '|| 1
USING msg;
END;
$$ LANGUAGE plpgsql;
I'm trying to create a function to get a field value from multiple tables in my database. I made script like this:
CREATE OR REPLACE FUNCTION get_all_changes() RETURNS SETOF RECORD AS
$$
DECLARE
tblname VARCHAR;
tblrow RECORD;
row RECORD;
BEGIN
FOR tblrow IN SELECT tablename FROM pg_catalog.pg_tables WHERE schemaname='public' LOOP /*FOREACH tblname IN ARRAY $1 LOOP*/
RAISE NOTICE 'r: %', tblrow.tablename;
FOR row IN SELECT MAX("lastUpdate") FROM tblrow.tablename LOOP
RETURN NEXT row;
END LOOP;
END LOOP;
END
$$
LANGUAGE 'plpgsql' ;
SELECT get_all_changes();
But it is not working, everytime it shows this error
tblrow.tablename" not defined in line "FOR row IN SELECT MAX("lastUpdate") FROM tblrow.tablename LOOP"
Your inner FOR loop must use the FOR...EXECUTE syntax as shown in the manual:
FOR target IN EXECUTE text_expression [ USING expression [, ... ] ] LOOP
statements
END LOOP [ label ];
In your case something along this line:
FOR row IN EXECUTE 'SELECT MAX("lastUpdate") FROM ' || quote_ident(tblrow.tablename) LOOP
RETURN NEXT row;
END LOOP
The reason for this is explained in the manual somewhere else:
Oftentimes you will want to generate dynamic commands inside your PL/pgSQL functions, that is, commands that will involve different tables or different data types each time they are executed. PL/pgSQL's normal attempts to cache plans for commands (as discussed in Section 39.10.2) will not work in such scenarios. To handle this sort of problem, the EXECUTE statement is provided[...]
Answer to your new question (mislabeled as answer):
This can be much simpler. You do not need to create a table just do define a record type.
If at all, you would better create a type with CREATE TYPE, but that's only efficient if you need the type in multiple places. For just a single function, you can use RETURNS TABLE instead :
CREATE OR REPLACE FUNCTION get_all_changes(text[])
RETURNS TABLE (tablename text
,"lastUpdate" timestamp with time zone
,nums integer) AS
$func$
DECLARE
tblname text;
BEGIN
FOREACH tblname IN ARRAY $1 LOOP
RETURN QUERY EXECUTE format(
$f$SELECT '%I', MAX("lastUpdate"), COUNT(*)::int FROM %1$I
$f$, tblname)
END LOOP;
END
$func$ LANGUAGE plpgsql;
A couple more points:
Use RETURN QUERY EXECUTE instead of the nested loop. Much simpler and faster.
Column aliases would only serve as documentation, those names are discarded in favor of the names declared in the RETURNS clause (directly or indirectly).
Use format() with %I to replace the concatenation with quote_ident() and %1$I to refer to the same parameter another time.
count() usually returns type bigint. Cast the integer, since you defined the column in the return type as such: count(*)::int.
Thanks,
I finally made my script like:
CREATE TABLE IF NOT EXISTS __rsdb_changes (tablename text,"lastUpdate" timestamp with time zone, nums bigint);
CREATE OR REPLACE FUNCTION get_all_changes(varchar[]) RETURNS SETOF __rsdb_changes AS /*TABLE (tablename varchar(40),"lastUpdate" timestamp with time zone, nums integer)*/
$$
DECLARE
tblname VARCHAR;
tblrow RECORD;
row RECORD;
BEGIN
FOREACH tblname IN ARRAY $1 LOOP
/*RAISE NOTICE 'r: %', tblrow.tablename;*/
FOR row IN EXECUTE 'SELECT CONCAT('''|| quote_ident(tblname) ||''') AS tablename, MAX("lastUpdate") AS "lastUpdate",COUNT(*) AS nums FROM ' || quote_ident(tblname) LOOP
/*RAISE NOTICE 'row.tablename: %',row.tablename;*/
/*RAISE NOTICE 'row.lastUpdate: %',row."lastUpdate";*/
/*RAISE NOTICE 'row.nums: %',row.nums;*/
RETURN NEXT row;
END LOOP;
END LOOP;
RETURN;
END
$$
LANGUAGE 'plpgsql' ;
Well, it works. But it seems I can only create a table to define the return structure instead of just RETURNS SETOF RECORD. Am I right?
Thanks again.
I have the following script that I want output to the screen from.
CREATE OR REPLACE FUNCTION randomnametest() RETURNS integer AS $$
DECLARE
rec RECORD;
BEGIN
FOR rec IN SELECT * FROM my_table LOOP
SELECT levenshtein('mystring',lower('rec.Name')) ORDER BY levenshtein;
END LOOP;
RETURN 1;
END;
$$ LANGUAGE plpgsql;
I want to get the output of the levenshein() function in a table along with the rec.Name. How would I do that? Also, it is giving me an error about the line where I call levenshtein(), saying that I should use perform instead.
Assuming that you want to insert the function's return value and the rec.name into a different table. Here is what you can do (create the table new_tab first)-
SELECT levenshtein('mystring',lower(rec.Name)) AS L_val;
INSERT INTO new_tab (L_val, rec.name);
The usage above is demonstrated below.
I guess, you can use RAISE INFO 'This is %', rec.name; to view the values.
CREATE OR REPLACE FUNCTION randomnametest() RETURNS integer AS $$
DECLARE
rec RECORD;
BEGIN
FOR rec IN SELECT * FROM my_table LOOP
SELECT levenshtein('mystring',lower(rec.Name))
AS L_val;
RAISE INFO '% - %', L_val, rec.name;
END LOOP;
RETURN 1;
END;
$$ LANGUAGE plpgsql;
Note- the FROM clause is optional in case you select from a function in a select like netxval(sequence_name) and don't have any actual table to select from i.e. like SELECT nextval(sequence_name) AS next_value;, in Oracle terms it would be SELECT sequence_name.nextval FROM dual; or SELECT function() FROM dual;. There is no dual in postgreSQL.
I also think that the ORDER BY is not necessary since my assumption would be that your function levenshtein() will most likely return only one value at any point of time, and hence wouldn't have enough data to ORDER.
If you want the output from a plpgsql function like the title says:
CREATE OR REPLACE FUNCTION randomnametest(_mystring text)
RETURNS TABLE (l_dist int, name text) AS
$BODY$
BEGIN
RETURN QUERY
SELECT levenshtein(_mystring, lower(t.name)), t.name
FROM my_table t
ORDER BY 1;
END;
$$ LANGUAGE plpgsql;
Declare the table with RETURNS TABLE.
Use RETURN QUERY to return records from the function.
Avoid naming conflicts between column names and OUT parameters (from the RETURNS TABLE clause) by table-qualifying column names in queries. OUT parameters are visible everywhere in the function body.
I made the string to compare to a parameter to the function to make this more useful.
There are other ways, but this is the most effective for the task. You need PostgreSQL 8.4 or later.
For a one-time use I would consider to just use a plain query (= function body without the RETURN QUERY above).