Hello i'm wondering why I can't use an SELECT in my SET of an UPDATE like this :
UPDATE "WU_Users" SET (SELECT "colonnesName" FROM colonnes WHERE "id" = i) = '0/0' WHERE "IDWU_Users" = (SELECT "idUser" FROM query WHERE "id" = i);
I get this error :
erreur de syntaxe sur ou près de « SELECT »
LIGNE 22 : UPDATE "WU_Users" SET (SELECT "colonnesName" FRO...
Apparently you are attempting to derive the column name to be updated from a column in another table. However, parsing an SQL statement requires the structural components (table names, column name, view names, ...) to be fixed before the statement can be parsed. What you are attempting would require parsing part of the statement inside parsing the statement. Currently, that is not going to happen. To accomplish what you are attempting will require dynamic SQL in order to generate the UPDATE statement at run time. Something like:
create or replace
procedure update_wu_users_from_idwu_users(i integer) -- assumes i as parameter as it is not defined
language plpgsql
as $$
declare
k_update_stmt constant text =
$stmt$ update wu_users set %I = '0/0'
where wu_users =
(select iduser
from query -- assumes query is a table, view, or materalized view
where id = i
)
$stmt$;
l_update_column text;
l_update_stmt text;
begin
select colonnesname
into l_update_column
from columns
where id = i;
if not found then
raise exception 'No column name found on table colonnes for id=%',i;
end if;
l_update_stmt = format(k_update_stmt,k_update_stmt);
raise notice '%', l_update_stmt; -- for debigging for prod raise_log might be better
execute l_update_stmt;
end;
$$;
NOTE: In the absence of table definition and test data the above IS NOT tested. Nor will I quarantine it complies. It is offered as example.
Related
I have a function that uses RECORD to temporarily store the data. I can use it - it's fine. My problem is that I can't hardcode columns I need to get from the RECORD. I must do it dynamically. Something line:
DECLARE
r1 RECORD;
r2 RECORD;
BEGIN
for r1 in Select column_name
from columns_to_process
where process_now = True
loop
for r2 in Select *
from my_data_table
where whatever
loop
-----------------------------
here I must call column by its name that is unknown at design time
-----------------------------
... do something with
r2.(r1.column_name)
end loop;
end loop;
END;
Does anyone know how to do it?
best regards
M
There is no need to select the all the qualifying rows and compute the total in a loop. Actually when working with SQL try to drop the word loop for your vocabulary; instead just use sum(column_name) in the select. The issue here is that you do not know what column to sum when the query is written, and all structural components(table names, columns names, operators, etc) must be known before submitting. You cannot use a variable for a structural component - in this case a column name. To do that you must use dynamic sql - i.e. SQL statement built by the process. The following accomplishes that: See example here.
create or replace function sum_something(
the_something text -- column name
, for_id my_table.id%type -- my_table.id
)
returns numeric
language plpgsql
as $$
declare
k_query_base constant text :=
$STMT$ Select sum(%I) from my_table where id = %s; $STMT$;
l_query text;
l_sum numeric;
begin
l_query = format(k_query_base, the_something, for_id);
raise notice E'Rumming Statememt:\n %',l_query; -- for prod raise Log
execute l_query into l_sum;
return l_sum;
end;
$$;
Well, after some time I figured out that I could use temporary table instead of RECORD. Doing so gives me all advantages of using dynamic queries so I can call any column by its name.
DECLARE
_my_var bigint;
BEGIN
create temporary table _my_temp_table as
Select _any, _column, _you, _need
from _my_table
where whatever = something;
execute 'Select ' || _any || ' from _my_temp_table' into _my_var;
... do whatever
END;
However I still believe that there should be a way to call records field by it's name.
I tried to run this script with the parameters in place but it keeps throwing syntax errors.Is there anything wrong with the syntax.Also what is the correct way to call this function.I require an output that tells me the update statement was executed successfully. I tried "select function_name(schema_name.TABLE_NAME);".Let me add that I am a beginner and am open to any kind of feedback. will also provide more details if necessary.
CREATE OR REPLACE FUNCTION function_name (TABLE_NAME IN character varying)
RETURNS text AS $SQLQuery$
DECLARE SQLQuery text;
BEGIN
SQLQuery =
' UPDATE '|| TABLE_NAME || ' SET column1=''0''
WHERE column1 is null;' ||
' UPDATE '|| TABLE_NAME || ' SET column2='value'
WHERE column2=''different value'';' ||
--multiple update statements later
Execute SQLQuery;
Return SQLQuery;
END;
$SQLQuery$
LANGUAGE plpgsql;
Update:
this is the error i am getting when i call the test function
ERROR: missing FROM-clause entry for table "schema_name"
LINE 2: select test_function(schema_name.TABLE_NAME);
^
********** Error **********
ERROR: missing FROM-clause entry for table "schema_name"
SQL state: 42P01
it is reading the function as a table?
I have also received syntax errors saying
EXECUTE column does not exist or that the function does not exist
even though i just declared it.
To use single quotes inside a siting constant, you must escape them by doubling them.
Instead of
' SET column1='0''
you'll have to write
' SET column1=''0'''
smth like:
CREATE OR REPLACE FUNCTION function_name (schema_name text,TABLE_NAME IN character varying)
RETURNS text AS $SQLQuery$
DECLARE
c int;
rtn text :='';
BEGIN
execute format(' UPDATE %I.%I SET column1=''0'' WHERE column1 is null;',schema_name,TABLE_NAME);
get diagnostics c = row_count;
raise info '%', 'affected: '||c;
rtn = rtn + 'affected: '||c||chr(10);
--repeat above construct for multiple update statement
return rtn;
END;
$SQLQuery$
LANGUAGE plpgsql;
and advises. I'm novice like you, but I learned to follow several rules, that help me:
with dynamic sql use format to avoid sql injection
don't overcomplicate things (eg the functionality you are looking for is inside UPDATE statement already - check the output. If you want to check the resulting row use, UPDATE ... RETURNING * construct.
practice is good, but reading concepts is precious.
In your POST select function_name(schema_name.TABLE_NAME); would not work, because you use schema_name.TABLE_NAME without quotes, but even if you put them, your function is vulnerable - what will happen if you run select function_name(';drop sometable;--');?..
You are trying to pass SQL Identifier, but your function takes string as parameter instead. You should change it to something like:
select test_function('schema_name.TABLE_NAME');
You can try that function below as base for whatever you are trying to do.
/* You need to split table and schema name
or you might get errors when using names that aren't lower case.
This: 'public.TEST1' would be translated to: "public.TEST1"
that is different table from public.test1
*/
CREATE OR REPLACE FUNCTION multi_update_stuff(schema_name varchar, table_name varchar)
/* We will return set of multiple columns. One possible method is to return table.
First column shows executed query, second if it returned no errors (true)
*/
RETURNS TABLE(SQLQuery text, result boolean)
AS $body$
DECLARE
/* Declare arroy of queries that we will iterate and execute later.
We use format() to build query from template and fill it with values.
%1$I can be described as "put first value here and treat it as object identifier"
%3$L can be described as "put third value here and treat it as SQL literal"
*/
SQLQueries text[] := array[
/* First query */
format('UPDATE %1$I.%2$I SET column1 = %3$L WHERE column1 is null;',
schema_name, table_name, '0'),
/* Second query */
format('UPDATE %1$I.%2$I SET column2 = %3$L WHERE column2 = %4$L;',
schema_name, table_name, 'value', 'different value'),
/* Third query, to see error free result */
'SELECT 1'];
BEGIN
/* Iterate our array */
FOREACH SQLQuery IN ARRAY SQLQueries
LOOP
/* Start transaction block */
BEGIN
EXECUTE SQLQuery;
result := true;
/* Catch error if any */
EXCEPTION
WHEN others THEN
result := false;
END;
/* Return row with whatever is assigned to variables listed in RETURNS.
In this case SQLQuery was already assigned by FOREACH.
*/
RETURN NEXT;
END LOOP;
END;
$body$
LANGUAGE plpgsql;
SELECT * FROM multi_update_stuff('schema_name', 'TABLE_NAME')
I have a trigger function that is called by several tables when COLUMN A is updated, so that COLUMN B can be updated based on value from a different function. (More complicated to explain than it really is). The trigger function takes in col_a and col_b since they are different for the different tables.
IF needs_updated THEN
sql = format('($1).%2$s = dbo.foo(($1).%1$s); ', col_a, col_b);
EXECUTE sql USING NEW;
END IF;
When I try to run the above, the format produces this sql:
($1).NameText = dbo.foo(($1).Name);
When I execute the SQL with the USING I am expecting something like this to happen (which works when executed straight up without dynamic sql):
NEW.NameText = dbo.foo(NEW.Name);
Instead I get:
[42601] ERROR: syntax error at or near "$1"
How can I dynamically update the column on the record/composite type NEW?
This isn't going to work because NEW.NameText = dbo.foo(NEW.Name); isn't a correct sql query. And I cannot think of the way you could dynamically update variable attribute of NEW. My suggestion is to explicitly define behaviour for each of your tables:
IF TG_TABLE_SCHEMA = 'my_schema' THEN
IF TG_TABLE_NAME = 'my_table_1' THEN
NEW.a1 = foo(NEW.b1);
ELSE IF TG_TABLE_NAME = 'my_table_2' THEN
NEW.a2 = foo(NEW.b2);
... etc ...
END IF;
END IF;
First: This is a giant pain in plpgsql. So my best recommendation is to do this in some other PL, such as plpythonu or plperl. Doing this in either of those would be trivial. Even if you don't want to do the whole trigger in another PL, you could still do something like:
v_new RECORD;
BEGIN
v_new := plperl_function(NEW, column_a...)
The key to doing this in plpgsql is creating a CTE that has what you need in it:
c_new_old CONSTANT text := format(
'WITH
NEW AS (SELECT (r).* FROM (SELECT ($1)::%1$s r) s)
, OLD AS (SELECT (r).* FROM (SELECT ($2)::%1$s r) s
'
, TG_RELID::regclass
);
You will also need to define a v_new that is a plain record. You could then do something like:
-- Replace 2nd field in NEW with a new value
sql := c_new_old || $$SELECT row(NEW.a, $3, NEW.c) FROM NEW$$
EXECUTE sql INTO v_new USING NEW, OLD, new_value;
I have this code, to add trigger for a View in my postgresql database
CREATE OR REPLACE FUNCTION changeCityProc() RETURNS TRIGGER AS $changeCity$
BEGIN
UPDATE vvs.tb_company SET city = "LAL" WHERE cardpresso.cardinfo.tb_company_city = vvs.tb_company.city;
RETURN null;
END;
$changeCity$ LANGUAGE plpgsql;
CREATE TRIGGER mytrigger
INSTEAD OF UPDATE ON
cardpresso.cardinfo FOR EACH ROW EXECUTE PROCEDURE changeCityProc();
pgAdmin says "syntax error at or near "INSTEAD""
Let's simplify this. First, the two schemas.
CREATE SCHEMA cardpresso;
CREATE SCHEMA vvs;
Next, the simplest possible table.
CREATE TABLE vvs.tb_company
(
city character varying(25)
);
INSERT INTO vvs.tb_company VALUES ('foo');
And a fairly useless view.
CREATE VIEW cardpresso.cardinfo AS
SELECT 'test' as tb_company_city UNION ALL
SELECT 'Orem' UNION ALL
SELECT 'Wibble'
;
Simplify the function. Warning: This will destructively update the table. Be careful if you copy stuff from this function into something headed for production.
CREATE OR REPLACE FUNCTION changecityproc()
RETURNS trigger AS
$BODY$
BEGIN
UPDATE vvs.tb_company SET city = 'bar';
RETURN null;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
Finally, the trigger.
CREATE TRIGGER mytrigger
INSTEAD OF UPDATE
ON cardpresso.cardinfo
FOR EACH ROW
EXECUTE PROCEDURE changecityproc();
Now, if we update the view, we'd expect all the rows in vvs.tb_company to change to 'bar'.
select * from vvs.tb_company;
city
--
foo
update cardpresso.cardinfo
set tb_company_city = 'wibble';
select * from vvs.tb_company;
city
--
bar
So it looks like the problem is in the UPDATE statement of your function.
UPDATE vvs.tb_company SET city = "LAL"
WHERE cardpresso.cardinfo.tb_company_city = vvs.tb_company.city;
I'm not certain what you intended that statement to do, but it's not valid in PostgreSQL, regardless of whether "LAL" is supposed to be a column name or a string literal. As a string literal, 'LAL', it will raise an error.
ERROR: missing FROM-clause entry for table "cardinfo"
LINE 2: WHERE cardpresso.cardinfo.tb_company_city = vvs.tb_compa...
i have a variable that is a name of a table. How can i select or update from this using variable in query , for example:
create or replace function pg_temp.testtst ()
returns varchar(255) as
$$
declare
r record; t_name name;
begin
for r in SELECT tablename FROM pg_tables WHERE schemaname = 'public' limit 100 loop
t_name = r.tablename;
update t_name set id = 10 where id = 15;
end loop;
return seq_name;
end;
$$
language plpgsql;
it shows
ERROR: relation "t_name" does not exist
Correct reply is a comment from Anton Kovalenko
You cannot use variable as table or column name in embedded SQL ever.
UPDATE dynamic_table_name SET ....
PostgreSQL uses a prepared and saved plans for embedded SQL, and references to a target objects (tables) are deep and hard encoded in plans - a some characteristics has significant impact on plans - for one table can be used index, for other not. Query planning is relatively slow, so PostgreSQL doesn't try it transparently (without few exceptions).
You should to use a dynamic SQL - a one purpose is using for similar situations. You generate a new SQL string always and plans are not saved
DO $$
DECLARE r record;
BEGIN
FOR r IN SELECT table_name
FROM information_schema.tables
WHERE table_catalog = 'public'
LOOP
EXECUTE format('UPDATE %I SET id = 10 WHERE id = 15', r.table_name);
END LOOP;
END $$;
Attention: Dynamic SQL is unsafe (there is a SQL injection risks) without parameter sanitization. I used a function "format" for it. Other way is using "quote_ident" function.
EXECUTE 'UPDATE ' || quote_ident(r.table_name) || 'SET ...