I want to create procedure to use limit option either insert into.. with select.. or create table as select.....
I want to use limit to insert only 500K records at a time so I am using while loop I set count3 this time as i am trying to insert 1.5mil records.
call proc1( with long sql statement......................)
DELIMITER //
CREATE PROCEDURE proc1(IN sqllines text)
BEGIN
DECLARE valFrom INT;
DECLARE valTo INT;
DECLARE count INt default 0;
SET #sqlin = sqllines;
SET valFrom = 0;
SET valTo = 500000;
SET #sql = ('#sqlin LIMIT valFrom , valTo');
WHILE count < 3
DO
PREPARE stmt from #sql;
EXECUTE stmt;
SET valFrom = valFrom+500000;
SET valTo = valTo+500000;
set count = count + 1;
END WHILE;
END;
//
DELIMITER ;
Sorry to say, but you cannot pass a variable into a dynamic-SQL statement in T-SQL.
You can find more information in a question that I myself posted here. The answer here has detailed solution on this.
Related
I have a procedure that returns multiple rows, but separately. Please take a look at its result:
I causes some issues when I want to fetch the result in the code (backend side). Now I want to create a temporary table and insert all rows inside it and then return that temp table as the result of the stored procedure. How can I do that inside procedure?
Not sure it above idea is a good idea .. that's the only thing I can probably be useful to merge all rows all in one table as SP's result.
Here is my current procedure:
DELIMITER $$
CREATE DEFINER=`administrator`#`localhost` PROCEDURE `lending_ewallets_balance_in_merchant`(IN `user_id_param` BIGINT UNSIGNED, IN `business_id_param` INT UNSIGNED)
NO SQL
BEGIN
DECLARE dossier_id INT;
DECLARE query_string VARCHAR(255) DEFAULT '';
DECLARE cursor_List_isdone BOOLEAN DEFAULT FALSE;
DECLARE user_dossiers CURSOR FOR
Select ld.id, lwp.query_string
FROM lending_users_dossiers ld
JOIN lending_where_to_pays lwp ON ld.lending_where_to_pay_id = lwp.id
WHERE user_id = user_id_param
AND (ld.status = 'activated' OR ld.status = 'finished');
# 'finished' is for loans
DECLARE CONTINUE HANDLER FOR NOT FOUND SET cursor_List_isdone = TRUE;
Open user_dossiers;
loop_List: LOOP
FETCH user_dossiers INTO dossier_id, query_string;
IF cursor_List_isdone THEN
LEAVE loop_List;
END IF;
SET #qry = CONCAT(
"SELECT ld.id lending_dossier_id, ld.type, SUM(let.credit) balance
FROM lending_users_dossiers ld
JOIN lending_ewallet_transactions let
ON ld.id = let.lending_dossier_id
WHERE ld.id = ", dossier_id,
" AND ", business_id_param, " IN(", query_string, ")",
"GROUP BY ld.id, ld.type");
PREPARE stmt FROM #qry;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END LOOP loop_List;
Close user_dossiers;
END$$
DELIMITER ;
Noted that, the MySQL version I use is MySQL v8.0.20.
The logic should be something like this. Outside the loop create a temp table if not exists and delete the data from it:
CREATE TEMPORARY TABLE
IF NOT EXISTS
user_dossiers_tmp (your columns);
DELETE FROM user_dossiers_tmp;
In your loop:
INSERT INTO user_dossiers_tmp VALUES (your data);
After your loop:
SELECT * FROM user_dossiers_tmp;
END$$
I intend to write a procedure to run a query on each of the tables in a provided list (can be a comma separated list or a table - undecided on that yet)
I started off with creating a while loop to iterate through each element in the provided list. Have been able to extract each element but I don't know how to run a query for that extracted element/table.
DELIMITER $$
DROP PROCEDURE IF EXISTS retain_demo_clients$$
CREATE PROCEDURE retain_demo_clients()
BEGIN
DECLARE counter INT(10);
DECLARE client_tables VARCHAR(255);
DECLARE table_count INT(10);
DECLARE table_in_process VARCHAR(255);
SET counter = 1;
SET table_count = 3;
SET client_tables = 'client_table, somerandomstuff, somemorestuff';
WHILE (counter < table_count +1) DO
SET table_in_process = substring_index(substring_index(client_tables, ',',counter),',',-1);
SELECT table_in_process;
SET counter = counter +1;
END WHILE;
END$$
DELIMITER ;
CALL retain_demo_clients();
I expect to do something like 'select * from table_in_process'. Would also appreciate if there is a better way to loop through the list of tables.
Here is DBFiddle link, if someone wants to tinker: https://www.db-fiddle.com/f/v6EMsiWvXFrBoNLgoZwDVX/1
You can use EXECUTE to run a text that represent a single statement
SET #someQuery = CONCAT('SELECT * FROM ', table_in_process ) ;
PREPARE preparable_stmt FROM #someQuery;
EXECUTE preparable_stmt;
I am trying to create function inside MySQL to create several queries for example :
DELIMITER |
CREATE PROCEDURE queryBuilder(_tableName varchar(100))
BEGIN
SET #str_query = 'SET #countRows = 0;SELECT COUNT(*) INTO #countRows FROM';
SET #str_query = CONCAT(#str_query,_tableName, '; SELECT #countRows');
PREPARE stmt1 FROM #str_query;
EXECUTE stmt1;
END|
DELIMITER;
but it doesn't work? how can i change to work? I know i can create IF statement but i want something with more flexibility.
I think you need to declare that variable before you set it. (I also chose not to use a reserved word in MySQL, i.e. 'count')
Like this (truncated):
BEGIN
DECLARE rowCount INT;
SET rowCount = 0;
SELECT COUNT(*) INTO rowCount from _tableName;
RETURN rowCount;
...
See examples like this: http://www.mysqltutorial.org/mysql-stored-function/
Hope that helps
Assuming a database with a ridiculous amount of tables (200+), how can I perform SELECT * FROM <> LIMIT 3; where <> represents all the tables in the database? My goal is to get an idea of what each table contains, and the column names shown in DESCRIBE are not particularly useful. Therefore I would like to see 3 records from each table.
I know that I could easily script this in PHP by iterating over the output of show tables; however I am looking for a command to run on the MySQL interpreter (mysql> prompt).
It's described in detail under this link (haven't tried it myself though, it's just in my bookmarks):
http://www.youdidwhatwithtsql.com/mysql-clone-of-sp_msforeachtable/624
DELIMITER $$
DROP PROCEDURE IF EXISTS `usp_mysql_foreachtable`$$
CREATE PROCEDURE `usp_mysql_foreachtable`(IN sql_string VARCHAR(1000))
LANGUAGE SQL
NOT DETERMINISTIC
COMMENT 'Functional clone of sp_MsForEachTable'
BEGIN
DECLARE var_tablename VARCHAR(100);
DECLARE last_row BIT;
DECLARE table_cursor CURSOR FOR SELECT TABLE_NAME
FROM information_schema.TABLES
WHERE TABLE_TYPE = 'BASE TABLE'
AND TABLE_SCHEMA = DATABASE();
DECLARE CONTINUE HANDLER FOR NOT FOUND SET last_row = 1;
OPEN table_cursor;
FETCH table_cursor INTO var_tablename;
SET last_row = 0;
SET #var = '';
lbl_table_cursor: LOOP
SET #qry = REPLACE(sql_string, '?', var_tablename);
PREPARE q FROM #qry;
EXECUTE q;
DEALLOCATE PREPARE q;
FETCH table_cursor INTO var_tablename;
IF last_row = 1 THEN
LEAVE lbl_table_cursor;
END IF;
END LOOP lbl_table_cursor;
CLOSE table_cursor;
END$$
DELIMITER ;
Then you call it with
CALL usp_mysql_foreachtable('SELECT * FROM ? LIMIT 3;');
I would like to use LIMIT in a cursor. The cursor should be used and updated several times within a loop, each time with different parameters of LIMIT. Here some code:
DELIMITER $$
CREATE PROCEDURE `updateIt`() READS SQL DATA
BEGIN
declare done int(1) default 0;
declare counter int(10) default 0;
declare xabc int(10) default 0;
declare tab1Cursor cursor for select abc from tab1 limit 100000*counter, 100000;
declare continue handler for not found set done=1;
loopCounter: LOOP
set done = 0;
open tab1Cursor;
igmLoop: loop
fetch tab1Cursor into xabc;
if done = 1 then leave igmLoop; end if;
-- do something
end loop igmLoop;
close tab1Cursor;
if (counter = 1039)
leave loopCounter;
end if;
set counter = counter + 1;
END LOOP loopCounter;
END $$
DELIMITER ;
This, however, does not work (I also tried it with the cursor in the LOOP counterLoop). Can Mysql deal with dynamic cursors?
From the MySQL Manual
a cursor cannot be used for a dynamic statement that is prepared and
executed with PREPARE and EXECUTE. The statement for a cursor is
checked at cursor creation time, so the statement cannot be dynamic.
However there are 2 ways, according to this post in mysql forums:
The first is for cases where absolutely only one user at a time will be running the procedure. A prepare statement can be used to create a view with the dynamic SQL and the cursor can select from this statically-named view. There's almost no performance impact. Unfortunately, these views are also visible to other users (there's no such thing as a temporary view), so this won't work for multiple users.
Analogously, a temporary table can be created in the prepare statement and the cursor can select from the temporary table. Only the current session can see a temporary table, so the multiple user issue is resolved. But this solution can have significant performance impact since a temp table has to be created each time the proc runs.
Bottom line: We still need cursors to be able to be created dynamically!
Here's an example of using a view to pass the table name and column name into a cursor.
DELIMITER //
DROP PROCEDURE IF EXISTS test_prepare//
CREATE PROCEDURE test_prepare(IN tablename varchar(255), columnname varchar(50))
BEGIN
DECLARE cursor_end CONDITION FOR SQLSTATE '02000';
DECLARE v_column_val VARCHAR(50);
DECLARE done INT DEFAULT 0;
DECLARE cur_table CURSOR FOR SELECT * FROM test_prepare_vw;
DECLARE CONTINUE HANDLER FOR cursor_end SET done = 1;
SET #query = CONCAT('CREATE VIEW test_prepare_vw as select ', columnname, ' from ', tablename);
select #query;
PREPARE stmt from #query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
OPEN cur_table;
FETCH cur_table INTO v_column_val;
WHILE done = 0 DO
SELECT v_column_val;
FETCH cur_table INTO v_column_val;
END WHILE;
CLOSE cur_table;
DROP VIEW test_prepare_vw;
END;
//
DELIMITER ;