I need to construct and execute an UPDATE statement dynamically. Then I need to test whether anything was updated at all. My code is as follows:
DECLARE
v_table_name text;
v_column_name text;
v_debug_flag boolean;
v_upd_stmt text;
BEGIN
select nm_table_name, replace(nm_table_name, 'CDB_', 'ID_')
into strict v_table_name, v_column_name
from m_entity e
where id=12;
v_upd_stmt := format('update %s set id_lock_usr =null, dt_lock=null where %s=$1 returning id_lock_usr',
v_table_name,
v_column_name);
execute v_upd_stmt using p_id;
END
How to know if anything was updated?
How to know if anything was updated ?
Various options. In a plpgsql function, you can check the special variable FOUND to see if the last SQL command affected any rows.
IF FOUND THEN ...
However, For dynamic queries with EXECUTE use GET DIAGNOSTICS instead. The manual:
Note in particular that EXECUTE changes the output of GET DIAGNOSTICS,
but does not change FOUND.
Related:
Dynamic SQL (EXECUTE) as condition for IF statement
Aside:
I see lingering problems with properly escaped identifiers (especially with upper case table names like you have), possibly even SQL injection. Fix with:
DECLARE
v_table_name text;
v_column_name text;
v_id_lock_usr integer; -- guessing the data type
i integer;
BEGIN
SELECT nm_table_name, replace(nm_table_name, 'CDB_', 'ID_')
INTO strict v_table_name, v_column_name
FROM m_entity e
WHERE id = 12;
EXECUTE format('UPDATE %I SET id_lock_usr = null, dt_lock = null
WHERE %I = $1 RETURNING id_lock_usr'
, v_table_name,
, v_column_name)
INTO v_id_lock_usr; -- to store the *single* result from RETURNING
GET DIAGNOSTICS i = ROW_COUNT;
IF i > 0 THEN
-- do something
END IF;
END
Note %I instead of %s.
In your case, if id_lock_usr returned by your query is NOT NULL (reliably), you might just test the result directly instead:
IF v_id_lock_usr IS NOT NULL ...
And you might want to schema-qualify table names to avoid ambiguities. But you must escape schema_name.table_name as two separate identifiers ..
Related:
Are PostgreSQL column names case-sensitive?
Define table and column names as arguments in a plpgsql function?
Table name as a PostgreSQL function parameter
Related
How can I write a stored procedure that contains a dynamically built SQL statement that returns a result set? Here is my sample code:
CREATE OR REPLACE FUNCTION reporting.report_get_countries_new (
starts_with varchar,
ends_with varchar
)
RETURNS TABLE (
country_id integer,
country_name varchar
) AS
$body$
DECLARE
starts_with ALIAS FOR $1;
ends_with ALIAS FOR $2;
sql VARCHAR;
BEGIN
sql = 'SELECT * FROM lookups.countries WHERE lookups.countries.country_name >= ' || starts_with ;
IF ends_with IS NOT NULL THEN
sql = sql || ' AND lookups.countries.country_name <= ' || ends_with ;
END IF;
RETURN QUERY EXECUTE sql;
END;
$body$
LANGUAGE 'plpgsql'
VOLATILE
CALLED ON NULL INPUT
SECURITY INVOKER
COST 100 ROWS 1000;
This code returns an error:
ERROR: syntax error at or near "RETURN"
LINE 1: RETURN QUERY SELECT * FROM omnipay_lookups.countries WHERE o...
^
QUERY: RETURN QUERY SELECT * FROM omnipay_lookups.countries WHERE omnipay_lookups.countries.country_name >= r
CONTEXT: PL/pgSQL function "report_get_countries_new" line 14 at EXECUTE statement
I have tried other ways instead of this:
RETURN QUERY EXECUTE sql;
Way 1:
RETURN EXECUTE sql;
Way 2:
sql = 'RETURN QUERY SELECT * FROM....
/*later*/
EXECUTE sql;
In all cases without success.
Ultimately I want to write a stored procedure that contains a dynamic sql statement and that returns the result set from the dynamic sql statement.
There is room for improvements:
CREATE OR REPLACE FUNCTION report_get_countries_new (starts_with text
, ends_with text = NULL)
RETURNS SETOF lookups.countries AS
$func$
DECLARE
sql text := 'SELECT * FROM lookups.countries WHERE country_name >= $1';
BEGIN
IF ends_with IS NOT NULL THEN
sql := sql || ' AND country_name <= $2';
END IF;
RETURN QUERY EXECUTE sql
USING starts_with, ends_with;
END
$func$ LANGUAGE plpgsql;
-- the rest is default settings
Major points
PostgreSQL 8.4 introduced the USING clause for EXECUTE, which is useful for several reasons. Recap in the manual:
The command string can use parameter values, which are referenced in
the command as $1, $2, etc. These symbols refer to values supplied in
the USING clause. This method is often preferable to inserting data
values into the command string as text: it avoids run-time overhead of
converting the values to text and back, and it is much less prone to
SQL-injection attacks since there is no need for quoting or escaping.
IOW, it is safer and faster than building a query string with text representation of parameters, even when sanitized with quote_literal().
Note that $1, $2 in the query string refer to the supplied values in the USING clause, not to the function parameters.
While you return SELECT * FROM lookups.countries, you can simplify the RETURN declaration like demonstrated:
RETURNS SETOF lookups.countries
In PostgreSQL there is a composite type defined for every table automatically. Use it. The effect is that the function depends on the type and you get an error message if you try to alter the table. Drop & recreate the function in such a case.
This may or may not be desirable - generally it is! You want to be made aware of side effects if you alter tables. The way you have it, your function would break silently and raise an exception on it's next call.
If you provide an explicit default for the second parameter in the declaration like demonstrated, you can (but don't have to) simplify the call in case you don't want to set an upper bound with ends_with.
SELECT * FROM report_get_countries_new('Zaire');
instead of:
SELECT * FROM report_get_countries_new('Zaire', NULL);
Be aware of function overloading in this context.
Don't quote the language name 'plpgsql' even if that's tolerated (for now). It's an identifier.
You can assign a variable at declaration time. Saves an extra step.
Parameters are named in the header. Drop the nonsensical lines:
starts_with ALIAS FOR $1;
ends_with ALIAS FOR $2;
Use quote_literal() to avoid SQL injection (!!!) and fix your quoting problem:
CREATE OR REPLACE FUNCTION report_get_countries_new (
starts_with varchar,
ends_with varchar
)
RETURNS TABLE (
country_id integer,
country_name varchar
) AS
$body$
DECLARE
starts_with ALIAS FOR $1;
ends_with ALIAS FOR $2;
sql VARCHAR;
BEGIN
sql := 'SELECT * FROM lookups.countries WHERE lookups.countries.country_name ' || quote_literal(starts_with) ;
IF ends_with IS NOT NULL THEN
sql := sql || ' AND lookups.countries.country_name <= ' || quote_literal(ends_with) ;
END IF;
RETURN QUERY EXECUTE sql;
END;
$body$
LANGUAGE 'plpgsql'
VOLATILE
CALLED ON NULL INPUT
SECURITY INVOKER
COST 100 ROWS 1000;
This is tested in version 9.1, works fine.
I am trying to create a dynamic function to use for setting up triggers.
CREATE OR REPLACE FUNCTION device_bid_modifiers_count_per()
RETURNS TRIGGER AS
$$
DECLARE
devices_count INTEGER;
table_name regclass := TG_ARGV[0];
column_name VARCHAR := TG_ARGV[1];
BEGIN
LOCK TABLE device_types IN EXCLUSIVE MODE;
EXECUTE format('LOCK TABLE %s IN EXCLUSIVE MODE', table_name);
SELECT INTO devices_count device_types_count();
IF TG_OP = 'DELETE' THEN
SELECT format(
'PERFORM validate_bid_modifiers_count(%s, %s, OLD.%s, %s)',
table_name,
column_name,
column_name,
devices_count
);
ELSE
SELECT format(
'PERFORM validate_bid_modifiers_count(%s, %s, NEW.%s, %s)',
table_name,
column_name,
column_name,
devices_count
);
END IF;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
My issue is with the execution of the dynamic function validate_bid_modifiers_count(). Currently it throws:
ERROR: query has no destination for result data
HINT: If you want to discard the results of a SELECT, use PERFORM instead.
CONTEXT: PL/pgSQL function device_bid_modifiers_count_per() line 21 at SQL statement
I can't really wrap my head around this. I understand that format() returns the correct string of function call with arguments. How do I fix this and make it work?
This should do it:
CREATE OR REPLACE FUNCTION device_bid_modifiers_count_per()
RETURNS TRIGGER AS
$func$
DECLARE
devices_count int := device_types_count();
table_name regclass := TG_ARGV[0];
column_name text := TG_ARGV[1];
BEGIN
LOCK TABLE device_types IN EXCLUSIVE MODE;
EXECUTE format('LOCK TABLE %s IN EXCLUSIVE MODE', table_name);
IF TG_OP = 'DELETE' THEN
PERFORM validate_bid_modifiers_count(table_name
, column_name
, (row_to_json(OLD) ->> column_name)::bigint
, devices_count);
ELSE
PERFORM validate_bid_modifiers_count(table_name
, column_name
, (row_to_json(NEW) ->> column_name)::bigint
, devices_count);
END IF;
RETURN NEW;
END
$func$ LANGUAGE plpgsql;
The immediate cause for the error message was the outer SELECT. Without target, you need to replace it with PERFORM in plpgsql. But the inner PERFORM in the query string passed to EXECUTE was wrong, too. PERFORM is a plpgsql command, not valid in an SQL string passed to EXECUTE, which expects SQL code. You have to use SELECT there. Finally OLD and NEW are not visible inside EXECUTE and would each raise an exception of their own the way you had it. All issues are fixed by dropping EXECUTE.
A simple and fast way to get the value of a dynamic column name from the row types OLD and NEW: cast to json, then you can parameterize the key name like demonstrated. Should be a bit simpler and faster than the alternative with dynamic SQL - which is possible as well, like:
...
EXECUTE format('SELECT validate_bid_modifiers_count(table_name
, column_name
, ($1.%I)::bigint
, devices_count)', column_name)
USING OLD;
...
Related:
Get values from varying columns in a generic trigger
Trigger with dynamic field name
Aside: Not sure why you need the heavy locks.
Aside 2: Consider writing a separate trigger function for each trigger instead. More noisy DDL, but simpler and faster to execute.
As I pointed out in the comment to Erwin Brandstetter's answer, initially I have an almost identical solution.
But issue was that I was getting the error
ERROR: record "new" has no field "column_name"
CONTEXT: SQL statement "SELECT validate_bid_modifiers_count(table_name, column_name, NEW.column_name, devices_count)"
PL/pgSQL function device_bid_modifiers_count_per() line 15 at PERFORM
This is why I thought I needed a way to dynamically evaluate things.
Currently got this working with the following still ugly looking to me solution (ugly because I don't like 2 IF statements, I would like it to be super dynamic, but maybe I am asking for too much):
CREATE OR REPLACE FUNCTION device_bid_modifiers_count_per()
RETURNS TRIGGER AS
$func$
DECLARE
row RECORD;
table_name regclass := TG_ARGV[0];
column_name text := TG_ARGV[1];
devices_count INTEGER;
BEGIN
LOCK TABLE device_types IN EXCLUSIVE MODE;
EXECUTE format('LOCK TABLE %s IN EXCLUSIVE MODE', table_name);
devices_count := device_types_count();
IF TG_OP = 'DELETE' THEN
row := OLD;
ELSE
row := NEW;
END IF;
IF column_name = 'campaign_id' THEN
PERFORM validate_bid_modifiers_count(table_name, column_name, row.campaign_id, devices_count);
ELSIF column_name = 'adgroup_id' THEN
PERFORM validate_bid_modifiers_count(table_name, column_name, row.adgroup_id, devices_count);
ELSE
RAISE EXCEPTION 'invalid_column_name %', column_name;
END IF;
RETURN NEW;
END;
$func$ LANGUAGE plpgsql;
I am open to more robust solution suggestions.
Basically, the second condition kind'a almost defeats the purpose of having a single function, I could have at this point as well split it into two functions. Because the goal is to define multiple (2) triggers using this function (providing arguments to it).
What would be the PL/SQL equivalent of this SQL query:
SELECT * FROM table(OWNER.PACKAGE.get_exam('123456789'));
This is the Function that I am trying to call:
FUNCTION get_exam(id IN VARCHAR2)
RETURN ab_assign_v1
IS
CURSOR c_exams(cid VARCHAR2) IS
SELECT t_api_exam_v1(
sei.person_id, --unique id
l.description --loc description
)
FROM my_view sei
JOIN loc l
ON sei.loc_code = l.loc_code
v_collection ab_assign_v1;
BEGIN
OPEN c_exams(id);
FETCH c_exams BULK COLLECT INTO v_collection;
CLOSE c_exams;
RETURN v_collection;
EXCEPTION
WHEN OTHERS THEN
error_a1.raise_error(SQLCODE, SQLERRM);
END get_exam;
Hope this helps.
DECLARE
lv <COLLECTION_NAME>;
BEGIN
lv:= OWNER.PACKAGE.get_exam('123456789');
dbms_output.put_line(lv.COUNT);
END;
/
Assuming that you want to return the result of a function :
select owner.package.get_exam('123456789') from table
Your function returns a nested table type. You simply need to declare a variable of that type, and assign to it as you would if it were a scalar:
declare
l_coll your_collection_type;
begin
l_coll := OWNER.PACKAGE.get_exam('123456789');
end;
/
In this example your_collection_type is a placeholder for whatever object your function actually returns.
" I am getting this error: PLS-00201: identifier 'ab_assign_v1' must be declared "
ab_assign_v1 is the type used by your function. From the code posted in your revised question it seems that type is in the same schema which owns the package with the function. However your original pseudo-code prefixes the call with the schema name. So, putting two and two together, you need to revise the variable declaration to include the schema too. (You may need to grant EXECUTE on it too, if you haven't done this already).
declare
l_coll OWNER.ab_assign_v1;
begin
l_coll := OWNER.PACKAGE.get_exam('123456789');
end;
/
I am familiar with MSSQL and using a parameter within the query, but I am not sure how I would do this within PL/SQL.
DECLARE
LSITEID NUMBER := 100001;
BEGIN
SELECT * from invoicehead ih
JOIN sitemaster sm on sm.SITEIID = ih.SITEIID
JOIN invoiceline il on il.invoiceIID = ih.invoiceIID
WHERE
ih.StartDate BETWEEN '2015-12-01' AND '2016-03-07'
AND SITEIID IN ( LSITEID)
END;
Right now I am testing this within Pl/SQL. But essentially I would be passing in the query with the parameter from MSSQL Linked Server OPENQuery.
How I can run the above query in PL/SQL with the parameter?
There is plenty of other resource for finding an answer, e.g. here (Tutorialspoint) or specifically here (plsql-tutorial). But perhaps I have missed your point.
To not remain on merely citing links, your query could look like this:
DECLARE
LSITEID integer;
BEGIN
LSITEID := 100001;
-- dostuff
END;
Two things to note: First, in a declare part (as I have learnt it) you should avoid assigning values. Second, if you intend to pass in different parameters you could/should use a procedure.
In PL/SQL you just use the name of the argument. In the following example, the argument is P_VALUE, note select statement says where dummy = p_value.
DECLARE
FUNCTION dummycount (p_value IN DUAL.dummy%TYPE)
RETURN INTEGER
AS
l_ret INTEGER;
BEGIN
SELECT COUNT (*) c
INTO l_ret
FROM DUAL
WHERE dummy = p_value;
RETURN l_ret;
END dummycount;
BEGIN
DBMS_OUTPUT.put_line ('A: ' || dummycount (p_value => 'A'));
DBMS_OUTPUT.put_line ('X: ' || dummycount (p_value => 'X'));
END;
This results in the following output:
A: 0
X: 1
I am working on PL/SQL code where I need to perform a select query using variable as column name in where clause. Column names are stored in a table as varchar and I am using a loop to pass those column names to my select statement.
Please find sample code segment I am trying to run:
set serveroutput on;
declare
var varchar2(100);
counter number;
begin
var:='description';
select count(*)
into counter
from nodetable
where var like '%Ship%';
dbms_output.put_line(counter);
end;
Output:
anonymous block completed
0
However the result should be 86.
Oracle is comparing last condition as two string and not column=string.
Please let me know if this is even feasible in oracle or if there is a workaround for it.
Regards
Ankit
You have to use dynamic SQL, preferrably with bind-variables:
EXECUTE IMMEDIATE
'select count(*) from nodetable where '||var||' like :p1'
INTO counter
USING '%Ship%';
Try this
declare
var varchar2(100);
counter number;
begin
var:='description';
EXECUTE IMMEDIATE
'select count(*)
into counter
from nodetable
where '||var||' like ''%Ship%'' ';
dbms_output.put_line(counter);
end;
You need to be carefull with the colon's (').
I agreed with previous answer in implementation, but i strictly recommend you to change your technical requirements, because you can't use bind variables for this, and it's potential place for injection. For example, if someone will edit value in your table which stores column names, to something like that: "description = inject_function or description". Then your dynamic sql block will execute this statement:
select count(*) from nodetable where description = inject_function or description like '%Ship%
and example implementation of function
create function inject_function
return varchar2
is pragma autonomous_transaction;
begin
delete * from most_important_table;
commit;
return to_char(null);
exception when others then
rollback;
return to_char(null);
end;