I have a stored procedure that insert data related to a scooter rent, one of the fields is a "rent code" when i insert the information "rent code" should be a unique random number that don exist in the table "rents"
here is that i tried
SELECT FLOOR(RAND() *9999)+1 AS random_num
FROM reservaciones
WHERE "random_num" NOT IN (SELECT reservaciones.Codigo_Reservacion FROM reservaciones)
LIMIT 1
in the table i got
1
2
3
when i run the code if i reduce the limit to 4 (example) the query still generates the numbers that i already got in my table
Create and use user-defined function similar to:
CREATE FUNCTION generate_random_number (upper_limit INT)
RETURNS INT
BEGIN
IF upper_limit = (SELECT COUNT(*) FROM main_table WHERE id <= upper_limit) THEN
RETURN NULL;
END IF;
IF upper_limit IS NULL THEN
SELECT REPEAT('9', LENGTH(MAX(id) + 1)) FROM main_table INTO upper_limit;
END IF;
RETURN (SELECT t1.id + 1
FROM (SELECT id FROM main_table
UNION ALL
SELECT 0) t1
LEFT JOIN main_table t2 ON t1.id = t2.id - 1
WHERE t2.id IS NULL
AND t1.id < upper_limit
ORDER BY RAND() LIMIT 1);
END
upper_limit parameter specifies the range from which the number should be generated. Can be less than max. existing value. Cannot be greater than 2147483647. Cannot be set to NULL if max. existing value is 999999999 or greater (you may expand this limit by set the parameter and output datatypes to BIGINT).
Function returns NULL if there is no free number in specified range.
fiddle with some comments.
Related
For my homework assignment, the stored procedure should accept an optional integer between 1 and 15, but default to 3 if no value is passed.
DELIMITER //
CREATE OR REPLACE PROCEDURE rankVideos(rank INT)
BEGIN
if rank = null then
SET rank = 3;
END if;
CREATE OR REPLACE TEMPORARY TABLE all_ranks AS (
SELECT * FROM youtube.homework7a
);
create OR REPLACE TEMPORARY TABLE t2 AS ( SELECT
category,
row_number() OVER (ORDER BY cnt DESC) v_cnt,
row_number() OVER (ORDER BY views DESC) v_views,
row_number() OVER (ORDER BY likes DESC) v_likes,
row_number() OVER (ORDER BY dislikes DESC) v_dislikes,
row_number() OVER (ORDER BY comment_count DESC) v_comment_count FROM all_ranks
);
CREATE OR REPLACE TEMPORARY TABLE t3 AS (
SELECT * FROM t2
WHERE v_cnt <= rank OR v_views <= rank OR v_likes <= rank
OR v_dislikes < rank OR v_comment_count <= rank
);
CREATE OR replace TEMPORARY TABLE t4 AS (
SELECT category,
case when v_cnt <= rank then v_cnt ELSE null END cnt,
case when v_views <= rank then v_views ELSE null END views,
case when v_likes <= rank then v_likes ELSE null END likes,
case when v_dislikes <= rank then v_dislikes ELSE null END dislikes,
case when v_comment_count <= rank then v_comment_count ELSE null END comment_count
FROM t3
)
;
SELECT *,
ifnull(cnt,999)
+ ifnull(views,999)
+ ifnull(likes,999)
+ ifnull(dislikes,999)
+ifnull(comment_count,999) num_non_null_cols,
ifnull(cnt,0)
+ ifnull(views,0)
+ ifnull(likes,0)
+ ifnull(dislikes,0)
+ ifnull(comment_count,0) sum_non_null_cols
FROM t4
ORDER BY num_non_null_cols, sum_non_null_cols;
END
//
DELIMITER ;
When I run the procedure and leave the integer blank I get an error that it has an incorrect integer value.
The syntax you show makes me think you are using MySQL or MariaDB.
These implementations don't support a feature for default values for procedure parameters. This has been requested in MySQL: https://bugs.mysql.com/bug.php?id=15975 But so far, it is not supported.
You're using the best workaround I know of, to set the parameter to your default value if it is NULL.
Another way of coding this is to use the COALESCE() function:
SET rank = COALESCE(rank, 3);
It's just another way to achieve the same thing that your IF/THEN code does.
SQL
MSSQL
create proc MyProc
#rank int = 3
as
...
GO
If you pass in a value, it will use that value. If you don't pass in a value, #rank = 3.
I get this error - 1241, operand should contain 1 column(s), upon running the query below:
select ifnull((select col1, col2 from table where uid = num limit 1) , '0');
If I project only 1 column it runs without error, I actually want to use select * to project all the columns, but it's not working for than one column, please suggest me something.
Try like this:-
select ifnull(col1,'0'), ifnull(col2,'0') from table where uid = num limit 1
You can't use ifnull over two column you could
or check for one column
select ifnull((select col1 from table where uid = num limit 1) , '0');
or use case for eval the content and return a single value
select ifnull((select case when col1 is null and col2 is null then null else 1 end
from table where uid = num limit 1) , '0');
How can I get the date for the latest value change in one column with one SQL query?
Possible database situation:
Date State
2012-11-25 state one
2012-11-26 state one
2012-11-27 state two
2012-11-28 state two
2012-11-29 state one
2012-11-30 state one
So result should return 2012-11-29 as latest change state. If I group by State value, I will get the date for first time I have that state in database.
The query will group the table on state and show the state and in the date field the latest date created of that state.
From the given input the output would be
Date State
2012-11-30 state one
2012-11-28 state two
This will get you the last state:
-- Query 1
SELECT state
FROM tableX
ORDER BY date DESC
LIMIT 1 ;
Encapsulating the above, we can use it to get the date just before the last change:
-- Query 2
SELECT t.date
FROM tableX AS t
JOIN
( SELECT state
FROM tableX
ORDER BY date DESC
LIMIT 1
) AS last
ON last.state <> t.state
ORDER BY t.date DESC
LIMIT 1 ;
And then use that to find the date (or the whole row) where the last change occurred:
-- Query 3
SELECT a.date -- can also be used: a.*
FROM tableX AS a
JOIN
( SELECT t.date
FROM tableX AS t
JOIN
( SELECT state
FROM tableX
ORDER BY date DESC
LIMIT 1
) AS last
ON last.state <> t.state
ORDER BY t.date DESC
LIMIT 1
) AS b
ON a.date > b.date
ORDER BY a.date
LIMIT 1 ;
Tested in SQL-Fiddle
And a solution that uses MySQL variables:
-- Query 4
SELECT date
FROM
( SELECT t.date
, #r := (#s <> state) AS result
, #s := state AS prev_state
FROM tableX AS t
CROSS JOIN
( SELECT #r := 0, #s := ''
) AS dummy
ORDER BY t.date ASC
) AS tmp
WHERE result = 1
ORDER BY date DESC
LIMIT 1 ;
I believe this is the answer:
SELECT
DISTINCT State AS State, `Date`
FROM
Table_1 t1
WHERE t1.`Date`=(SELECT MAX(`Date`) FROM Table_1 WHERE State=t1.State)
...and the test:
http://sqlfiddle.com/#!2/8b0d8/5
If you add another column 'changed datetime' you can fill this using an update trigger that inserts NOW(). If you query your table ordering on the changed column, it will endup first.
CREATE TRIGGER `trigger` BEFORE UPDATE ON `table`
FOR EACH ROW
BEGIN
SET ROW.changed = NOW();
END$$
Try this ::
Select
MAX(`Date`), state from mytable
group by state
If you had been using postgres, you could compare different rows in the same table using "LEAD .. OVER" I have not managed to find the same functionallity in mysql.
A bit hairy, but I think this will do:
select min(t1.date) from table_1 t1 where
(select count(distinct state) from table_1 where table_1.date>=t1.date)=1
Basically, this asks for the first time no changes in state is found for any later values. Be warned, it may be this query scales terribly for large data sets....
I think your best choice here are analytical functions. Try this - it should be OK performance-wise:
SELECT *
FROM test
WHERE my_date = (SELECT MAX (my_date)
FROM (SELECT MY_DATE
FROM ( SELECT MY_DATE,
STATE,
LAG (state) OVER (ORDER BY MY_DATE)
lag_val
FROM test
ORDER BY MY_DATE) a
WHERE state != lag_val))
In the inner select, the LAG function gets the previous value in the STATE column and in the outer select I mark the date of a change - those with lag value different than the current state value. And outside, I'm getting the latest date from those dates of a change... I hope that this is what you needed.
SELECT MAX(DATE) FROM YOUR_TABLE
Above answer doesn't seem to satisfy what OP needs.
UPDATED ANSWER WITH AFTER INSERT/UPDATE TRIGGER
DELCARE #latestState varchar;
DELCARE #latestDate date;
CREATE TRIGGER latestInsertTrigger AFTER INSERT ON myTable
FOR EACH ROW
BEGIN
IF OLD.DATE <> NEW.date THEN
SET #latestState = NEW.state
SET #latestDate = NEW.date
END IF
END
;
CREATE TRIGGER latestUpdateTrigger AFTER UPDATE ON myTable
FOR EACH ROW
BEGIN
IF OLD.DATE = NEW.date AND OLD.STATE <> NEW.STATE THEN
SET #latestState = NEW.state
SET #latestDate = NEW.date
END IF
END
;
You may use the following query to get the latest record added/updated:
SELECT DATE, STATE FROM myTable
WHERE STATE = #latestState
OR DATE = #latestDate
ORDER BY DATE DESC
;
Results:
DATE STATE
November, 30 2012 00:00:00+0000 state one
November, 28 2012 00:00:00+0000 state two
November, 27 2012 00:00:00+0000 state two
The above query results needs to be limitted to 2, 3 or n based on what you need.
Frankly it seems like you want to get max from both columns based on the data sample you have given. Assuming that your state only increases with the date. Only I wish if the state was an integer :D
Then union of two max sub queries on both columns would have solved it easily. Still a string manipulation regex can find what's the max in state column. Finally this approach needs limit x. However it still has lope hole. Anyway it took me sometime to figure your need out :$
I have two tables like this in mysql
a.cardnumber (unique)
a.position (numerical 3 digits or null)
a.serial
b.serial (unique)
b.lastused
I want to update any rows in "a" where position is above 600 AND "a.serial" is blank with any serial from "b.serial" where "b.lastused" is either null or more than 30 days ago. When the serial is copied into "a.serial" I want to update "b.lastused" with today's date so I know that the relevant "b.serial" has been used today.
There is no relation to the two tables apart from the serial and any serial from b can be used with any cardnumber in a.
I've tried this using my limited knowledge of mysql but I keep getting an error from my mysql desktop program to say I have an error in my query :(
Any help much appreciated!
I'm assuming here that you want to use a separate b.serial for each row to be updated in a. (This isn't specifically stated, but it seems to me to be most likely; please feel free to correct my assumption if it is wrong.)
I setup a small example. It wasn't clear what the datatypes for each of the columns, so I used INT where I wasn't sure. I used DATE datatype (rather than DATETIME) for lastused.
CREATE TABLE a (`cardnumber` VARCHAR(10) NOT NULL PRIMARY KEY, `position` INT, `serial` INT);
CREATE TABLE b (`serial` INT NOT NULL PRIMARY KEY, lastused DATE);
INSERT INTO a VALUES ('x0000',555,NULL),('x0001',700,123),('a1111',601,NULL),('a2222',602,NULL);
INSERT INTO b VALUES (100,'2012-07-15'),(101,NULL),(102,'2010-01-01'),(103,NULL),(104,NULL);
SELECT * FROM a;
SELECT * FROM b;
Based on the conditions you give, the rows with cardnumbers 'a1111' and 'a2222' should get updated, the other two rows should not (position <= 600, serial already assigned).
Before we run an UPDATE, we want to first run a SELECT that returns the rows to be updated, along with the values that will be assigned. Once we get that, we can convert that to a multi-table UPDATE statement.
SELECT a.cardnumber AS `a.cardnumber`
, a.position AS `a.position`
, a.serial AS `a.serial`
, b.serial AS `b.serial`
, b.lastused AS `b.lastused`
FROM (
SELECT #i := #i + 1 AS i
, aa.*
FROM a aa
JOIN (SELECT #i := 0) ii
WHERE aa.position > 600 /* assuming `position` is numeric datatype */
AND aa.serial IS NULL /* assuming 'blank' represented by NULL */
ORDER BY aa.cardnumber
) ia
JOIN (
SELECT #j := #j + 1 AS j
, bb.serial
, bb.lastused
FROM b bb
JOIN (SELECT #j := 0) jj
WHERE bb.lastused IS NULL
OR bb.lastused < DATE_ADD(NOW(),INTERVAL -30 DAY)
ORDER BY bb.serial
) jb
ON ia.i = jb.j
JOIN a ON a.cardnumber = ia.cardnumber
JOIN b ON b.serial = jb.serial
To convert that to an UPDATE, replace the SELECT ... FROM with UPDATE, and add a SET clause to assign new values to the tables.
UPDATE (
SELECT #i := #i + 1 AS i
, aa.*
FROM a aa
JOIN (SELECT #i := 0) ii
WHERE aa.position > 600
AND aa.serial IS NULL
ORDER BY aa.cardnumber
) ia
JOIN (
SELECT #j := #j + 1 AS j
, bb.serial
, bb.lastused
FROM b bb
JOIN (SELECT #j := 0) jj
WHERE bb.lastused IS NULL
OR bb.lastused < DATE_ADD(NOW(),INTERVAL -30 DAY)
ORDER BY bb.serial
) jb
ON ia.i = jb.j
JOIN a ON a.cardnumber = ia.cardnumber
JOIN b ON b.serial = jb.serial
SET a.serial = b.serial
, b.lastused = DATE(NOW())
-- 4 row(s) affected
You can run the queries for the inline views seperately (ia, jb) to verify that these are getting the rows you want to update.
The join from ia to a, and from jb to b, should be on the primary keys unique key.
The purpose of the ia and jb inline views is to get sequential numbers assigned to those rows so we can match them to each other.
The joins to a and b are to get back to the row in the original table, which is what we want to update.
(Obviously, some adjustments need to be made if serial is not an INT, or lastused is a DATETIME rather than a DATE.)
But this is an example of how I would go about doing the UPDATE you want to do (as best I understood it.)
NOTE: This approach works with MySQL versions that support subqueries. For MySQL 4.0, you would need to run this in steps, storing the results from the "ia" and "jb" inline views (subqueries) into actual tables. Then reference those tables in the query in place of the inline views. The ii and jj subqueries can be removed, and replaced with separate SELECT #i := 0, #j := 0 statement prior to the execution of the queries that reference these variables.
let me know if this works
Update table_a
set serial =
(
select b.serial from table_b b
where b.lastused = NULL
OR b.lastused < (current date - 30) limit 1
)
where cardnumber in
(
select a.cardnumber
from table_a a
where a.position > 600
and a.serial = NULL
)
update table_b b
set b.lastused = current date
where b.lastused = NULL
OR b.lastused < (current date - 30)
I have a table in a MySQL DB with an UNIQUE INT(10) column. The table is pretty populated and the row contains non-consecutive entries of Integer numbers in that column. I would like to do a query, which gets me the smallest number (or the n smallest numbers) that is not in any row.
Example: The table contains rows with values (1, 2, 3, 5, 7, 8, 10, 12, 15) for the column. The sql statement should return i.e. the five lowest non-contained values, which are 4, 6, 9, 11, 13 in this case.
Is this possible with MySQL?
You can use a "numbers" table (it's handy for various operations):
CREATE TABLE num
( i UNSIGNED INT NOT NULL
, PRIMARY KEY (i)
) ;
INSERT INTO num (i)
VALUES
(1), (2), ..., (1000000) ;
Then:
SELECT
num.i
FROM
num
LEFT JOIN
tableX AS t
ON num.i = t.columnX
WHERE
t.columnX IS NULL
ORDER BY
num.i
LIMIT 5
or:
SELECT
num.i
FROM
num
WHERE
NOT EXISTS
( SELECT *
FROM tableX AS t
WHERE num.i = t.columnX
)
ORDER BY
num.i
LIMIT 5
Another approach, without using an auxilary table, would be to use MySQL variables. You can test it in SQL-Fiddle, test-2. The output is not the same as the previous (just to show that it can be done):
SELECT start_id, end_id
FROM
( SELECT
IF( t.columnX <> #id, #id, NULL) AS start_id
, IF( t.columnX <> #id, t.columnX-1, NULL) AS end_id
, #rows := #rows + (t.columnX - #id) AS r
, #id := t.columnX + 1 AS running_id
FROM
tableX AS t
CROSS JOIN
( SELECT #rows := 0
, #id := 1
) AS dummy
WHERE
#rows < 5
ORDER BY
t.columnX
) AS tmp
WHERE
start_id IS NOT NULL
This will work, but I think it is pretty inefficient. You won't need an extra table though (a table that would be (2^31-1)*4/1024^3 = 8GB for all positive numbers in INT). Also I advise you look at why you need this, because it might not be neccesary.
Also it will return the start and end of a range, but not all numbers in that range. (e.g. if you have numbers 1 and 5 it will return {0,2,4,6})
SELECT (t.num-1) AS bound FROM t
WHERE t.num-1 NOT IN (SELECT t.num FROM t)
UNION
SELECT (t.num+1) AS bound FROM t
WHERE t.num+1 NOT IN (SELECT t.num FROM t)
As I said this will be pretty inefficient, JOINs might be faster but you would need benchmark it.
SELECT (t.num-1) AS bound FROM t
LEFT JOIN t AS u ON t.num-1 = u.num
WHERE u.num IS NULL
UNION
SELECT (t.num+1) AS bound FROM t
LEFT JOIN t AS u ON t.num+1 = u.num
WHERE u.num IS NULL