- Postgresql For Each Loop
- Python Postgresql Cursor
- Postgresql Function For Loop
- Postgresql Cursor For Loop Example Python
Use loops like this (there are more ways, but I think what you're doing is wrong): FOR row IN (query) LOOP END LOOP; Where 'row' is a variable of type RECORD. I'm not sure how this works with CURSOR, or if postgres 7.4 has different loop constructs, but you might want to look into that, in the documentation. Using PL/pgSQL for loop to iterate over a range of integers The following illustrates the syntax of the for loop statement that loops through a range of integers: for loopcounter in reverse from. To by step loop statements end loop label. PL/SQL Cursor Exercises: FETCH records with nested Cursors using Cursor FOR Loops Last update on February 26 2020 08:07:24 (UTC/GMT +8 hours) PL/SQL Cursor: Exercise-20 with Solution. In Oracle, cursors are taught as a part of programming 101. In many (if not most) cases, cursors are the first thing that the Oracle developer learns. The first class usually starts with: “There are 13 logical structures, the first of which is the loop, which goes like this” PostgreSQL, on the other hand, does not heavily rely on cursors. I am trying to declare select statement to cursor and then declare fields from Cursor to variables and then loop over them (the loop is fine, I have problem with cursor declaration ) having syntax errors on cursor.
Summary: in this tutorial, you will learn how to use the PL/SQL cursor
FOR LOOP
statement to fetch and process every record from a cursor.Introduction to PL/SQL cursor FOR LOOP
statement
The cursor
FOR LOOP
statement is an elegant extension of the numeric FOR LOOP
statement.The numeric
FOR LOOP
executes the body of a loop once for every integer value in a specified range. Similarly, the cursor FOR LOOP
executes the body of the loop once for each row returned by the query associated with the cursor.A nice feature of the cursor
FOR LOOP
statement is that it allows you to fetch every row from a cursor without manually managing the execution cycle i.e., OPEN
, FETCH
, and CLOSE
.The cursor
FOR LOOP
implicitly creates its loop index as a record variable with the row type in which the cursor returns and then opens the cursor.In each loop iteration, the cursor
FOR LOOP
statement fetches a row from the result set into its loop index. If there is no row to fetch, the cursor FOR LOOP
closes the cursor.The cursor is also closed if a statement inside the loop transfers control outside the loop, e.g.,
EXIT
and GOTO
, or raises an exception.The following illustrates the syntax of the cursor
FOR LOOP
statement:1) record
The
record
is the name of the index that the cursor FOR LOOP
statement declares implicitly as a %ROWTYPE
record variable of the type of the cursor.The
record
variable is local to the cursor FOR LOOP
statement. It means that you can only reference it inside the loop, not outside. After the cursor FOR LOOP
statement execution ends, the record
variable becomes undefined.2) cursor_name
The
cursor_name
is the name of an explicit cursor that is not opened when the loop starts.Postgresql For Each Loop
Note that besides the cursor name, you can use a
SELECT
statement as shown below:In this case, the cursor
FOR LOOP
declares, opens, fetches from, and closes an implicit cursor. However, the implicit cursor is internal; therefore, you cannot reference it.Note that Oracle Database automatically optimizes a cursor
FOR LOOP
to work similarly to a BULK COLLECT
query. Although your code looks as if it fetched one row at a time, Oracle Database fetches multiple rows at a time and allows you to process each row individually.PL/SQL cursor FOR LOOP
examples
Let’s look at some examples of using the cursor
FOR LOOP
statement to see how it works.A) PL/SQL cursor FOR LOOP
example
The following example declares an explicit cursor and uses it in the cursor
FOR LOOP
statement.In this example, the
SELECT
statement of the cursor retrieves data from the products
table. The FOR LOOP
statement opened, fetched each row in the result set, displayed the product information, and closed the cursor.B) Cursor FOR LOOP
with a SELECT
statement example
The following example is equivalent to the example above but uses a query in a cursor
FOR LOOP
statement.In this tutorial, you have learned how to use the PL/SQL cursor
FOR LOOP
to fetch data from a cursor.String sum and receiving multiple row result query in comma separated single row.
Execution result of the query in Postgresql Function
CREATE TABLE mem_reg_mcg
(
id serial NOT NULL,
br_id character varying(3) NOT NULL,
mid character varying(50) NOT NULL,
'name' character varying(200)
);
CREATE OR REPLACE FUNCTION get_all_single_row_mem(m_id integer)Execution result of the query in Postgresql Function
CREATE TABLE mem_reg_mcg
(
id serial NOT NULL,
br_id character varying(3) NOT NULL,
mid character varying(50) NOT NULL,
'name' character varying(200)
);
RETURNS character varying AS
$BODY$
DECLARE
_record RECORD;
alert_mesg character varying(2000);
IN_VAR1 character varying(50);
BEGIN
alert_mesg := ';
--Define output columns
FOR _record IN select m.name from mem_reg_mcg m where id> $1
LOOP
IN_VAR1 := _record.name;
--Build output string
alert_mesg := alert_mesg||IN_VAR1||', ';
END LOOP;
RETURN subString(alert_mesg,0,char_length(alert_mesg)-1);
--EXCEPTION -- WHEN OTHERS THEN -- RETURN 'No troubleshooting information at this time.';
Python Postgresql Cursor
END;Postgresql Function For Loop
$BODY$ LANGUAGE 'plpgsql' VOLATILE
COST 100;
ALTER FUNCTION get_all_single_row_mem(m_id integer) OWNER TO postgres;
Postgresql Cursor For Loop Example Python
See Cursor example