I'm fairly new to MySQL but I'd like to create a function to validate a JSON objects that are stored in my database tables.
I looked up information on creating a function, but must be missing something as I can't seem to get it to work. It doesn't seem like it would be overly complicated but perhaps I'm not using the appropriate syntax.
Here is my code:
DELIMITER //
CREATE FUNCTION CHECKJSON( DB_NAME varchar(255), TABLE_NAME varchar(255), JSON_COLUMN varchar(255))
RETURNS varchar(300)
BEGIN
DECLARE notNullCount int;
DECLARE validJSONCount int;
DECLARE result varchar(300);
SET notNullCount = (SELECT count(*) FROM DB_NAME.TABLE_NAME WHERE JSON_COLUMN IS NOT NULL);
set validJSONCount = (SELECT count(*) FROM DB_NAME.TABLE_NAME WHERE JSON_VALID(JSON_COLUMN) > 0);
CASE
WHEN (validJSONCount = notNullCount) THEN
SET result = CONCAT('VALID JSON COUNT: ', validJSONCount)
ELSE
SET result = CONCAT('INVALID JSON COUNT: ', (notNullCount - validJSONCount))
END;
RETURN result;
END //
DELIMITER ;
When I try to run this code, I get the following error message:
"Error Code: 1064. You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ELSE SET result = CONCAT('INVALID JSON COUNT: ', (notNullCount - validJSONC' at line 14"
Any thoughts on how I might improve this code? Thanks!
Since MySQL 5.7 you have a pretty and simple function for this:
JSON_VALID(value)
Returns 0 or 1 to indicate whether a value is valid JSON. Returns NULL if the argument is NULL.
https://dev.mysql.com/doc/refman/5.7/en/json-attribute-functions.html#function_json-valid
You're missing a couple of ; and to end the case it should be END CASE.
DELIMITER //
CREATE FUNCTION CHECKJSON( DB_NAME varchar(255), TABLE_NAME varchar(255), JSON_COLUMN varchar(255))
RETURNS varchar(300)
BEGIN
DECLARE notNullCount int;
DECLARE validJSONCount int;
DECLARE result varchar(300);
SET notNullCount = (SELECT count(*) FROM DB_NAME.TABLE_NAME WHERE JSON_COLUMN IS NOT NULL);
set validJSONCount = (SELECT count(*) FROM DB_NAME.TABLE_NAME WHERE JSON_VALID(JSON_COLUMN) > 0);
CASE
WHEN (validJSONCount = notNullCount) THEN
SET result = CONCAT('VALID JSON COUNT: ', validJSONCount) ;
ELSE
SET result = CONCAT('INVALID JSON COUNT: ', (notNullCount - validJSONCount)) ;
END CASE;
RETURN result;
END //
DELIMITER ;
Related
a MYSQL user defined function selects a row from a table. How does the UDF code determine if the selected row was found in the table?
CREATE FUNCTION snippetFolder_folderPath(folder_id int)
RETURNS varchar(512)
BEGIN
declare vFolder_id int;
declare vParent_id int;
declare vPath varchar(512) default '';
declare vFolderName varchar(256) default '';
set vFolder_id = folder_id;
build_path:
while (vFolder_id > 0) do
/* -------- how to know this select statement returns a row?? ---------- */
select a.parent_id, a.folderName
into vParent_id, vFolderName
from SnippetFolder a
where a.folder_id = vFolder_id;
if vPath = ' ' then
set vPath = vFolderName;
else
set vPath = concat_ws( '/', vFolderName, vPath );
end if ;
set vFolder_id = vParent_id;
end while ;
return vPath;
END
https://dev.mysql.com/doc/refman/8.0/en/select-into.html says:
If the query returns no rows, a warning with error code 1329 occurs (No data), and the variable values remain unchanged.
So you could declare a continue handler on warnings, something like the example from the documentation:
BEGIN
DECLARE i INT DEFAULT 3;
DECLARE done INT DEFAULT FALSE;
retry:
REPEAT
BEGIN
DECLARE CONTINUE HANDLER FOR SQLWARNING
BEGIN
SET done = TRUE;
END;
IF done OR i < 0 THEN
LEAVE retry;
END IF;
SET i = i - 1;
END;
UNTIL FALSE END REPEAT;
END
I'll leave it to you to read the documentation and adapt that example to your table and your loop.
Alternatively, if you're using MySQL 8.0 you can use recursive common table expression:
CREATE FUNCTION snippetFolder_folderPath(vFolder_id int)
RETURNS varchar(512)
BEGIN
DECLARE vPath varchar(512) DEFAULT '';
WITH RECURSIVE cte AS (
SELECT folderName, parent_id, 0 AS height
FROM SnippetFolder WHERE folder_id = vFolder_id
UNION
SELECT f.folderName, f.parent_id, cte.height+1
FROM SnippetFolder AS f JOIN cte ON cte.parent_id = f.folder_id
)
SELECT GROUP_CONCAT(folderName ORDER BY height DESC SEPARATOR '/')
INTO vPath
FROM cte;
RETURN vPath;
END
The recursive CTE result is all the ancestors of the row matching vFolder_id, and then one can use GROUP_CONCAT() to concatenate them together as one string.
I'm trying to transpose a postgres trigger to a mysql trigger. It automatically adds fields to the row according to the date added
CREATE FUNCTION convert_date ()
RETURNS trigger
AS $$
declare
date_min DATE;
date_max DATE;
temp_year INTEGER;
begin
SELECT SUBSTRING(NEW."dc_date_label",0,5)::integer
INTO temp_year;
SELECT date(temp_year || '-01-10')
INTO date_min;
SELECT date(temp_year +1 || '-09-30')
INTO date_max;
NEW."dc_date_start" = date_min;
NEW."dc_date_end" = date_max;
RETURN new;
end;
CREATE TRIGGER trig_b_i_compute_date()
BEFORE INSERT
ON campaigns
FOR EACH ROW
EXECUTE PROCEDURE convert_date();
This is what i've done on mysql :
DELIMITER //
CREATE TRIGGER trig_b_i_compute_date
BEFORE INSERT ON campaigns
FOR EACH ROW
BEGIN
DECLARE date_min DATE;
DECLARE date_max DATE;
DECLARE temp_year INTEGER;
SET temp_year = SELECT CONVERT( SUBSTRING(NEW.dc_date_label,1,5), UNSIGNED INTEGER) ;
SET date_min = SELECT CONVERT( CONCAT(temp_year,'-01-10'), DATE);
SET date_max = SELECT CONVERT( CONCAT(temp_year + 1, '09-30'), DATE);
SET NEW.dc_date_start = date_min;
SET NEW.dc_date_end = date_max;
END;
//
DELIMITER ;
However I get an error :
MySQL server version for the right syntax to use near 'SELECT CONVERT( SUBSTRING(NEW.dc_date_label,1,5), UNSIGNED INTEGER) ;
What is wrong with the procedure ?
If you use SELECT in a SET statement, you need to put it in parentheses:
SET temp_year = (SELECT ...);
But in your case you don't need a SELECT and you can just skip it:
SET temp_year = CONVERT(...);
You can also use the SELECT INTO syntax in MySQL:
SELECT CONVERT(...) INTO temp_year;
And there is no need to declare date_min and date_max. Also no need to cast everything explicitly. Your trigger body could be:
DECLARE temp_year INTEGER;
SET temp_year = CONVERT( SUBSTRING(NEW.dc_date_label,1,5), UNSIGNED);
SET NEW.dc_date_start = CONCAT(temp_year, '-01-10');
SET NEW.dc_date_end = CONCAT(temp_year + 1, '-09-30');
I don't know how dc_date_label looks like, and why the year should be 5 characters long. So I kept the year extraction as it is. But if it's a DATE, DATETIME or TIMESTAMP, you can just use the YEAR function:
SET temp_year = YEAR(NEW.dc_date_label);
And since it's much shorter, you could also use it inline and skip the temp_year variable:
SET NEW.dc_date_start = CONCAT(YEAR(NEW.dc_date_label), '-01-10');
SET NEW.dc_date_end = CONCAT(YEAR(NEW.dc_date_label) + 1, '-09-30');
And last one: Remove the semicolon after END. It might work, but it doesn't belong there.
I'm new to SQL programming and I decided to make a script. This one might be quite riddled with errors but I'm getting an error that I'm unable to resolve.
DELIMITER $
DROP FUNCTION IF EXISTS crossref$
CREATE FUNCTION crossref()
BEGIN
DECLARE i INT;
DECLARE names VARCHAR(70);
SET i = 1;
myloop: LOOP
SET i=i+1;
IF i = 6 then
LEAVE myloop;
END IF;
SET names = (SELECT NAME FROM cbase_excel_table WHERE ID = i);
INSERT INTO cbase_master(NAME, PERMALINK, HOMEPAGE_URL, CATEGORY_LIST, MARKET, FUNDING, 'STATUS', COUNTRY, REGION, CITY)
SELECT NAME, PERMALINK, HOMEPAGE_URL, CATEGORY_LIST, MARKET, FUNDING, 'STATUS', COUNTRY, REGION, CITY FROM cbase_excel_table WHERE ID = i;
UPDATE cbase_master
SET DESCRIPTION = (SELECT DESCRIPTION FROM cbase_json_table WHERE NAME = names)
SET DOMAIN = (SELECT DOMAIN FROM cbase_json_table WHERE NAME = names)
SET IMAGE_URL = (SELECT IMAGE_URL FROM cbase_json_table WHERE NAME = names)
SET FACEBOOK_URL = (SELECT FACEBOOK_URL FROM cbase_json_table WHERE NAME = names)
SET TWITTER_URL = (SELECT TWITTER_URL FROM cbase_json_table WHERE NAME = names)
SET LINKEDIN_URL = (SELECT LINKEDIN_URL FROM cbase_json_table WHERE NAME = names)
SET CBASE_UUID = (SELECT CBASE_UUID FROM cbase_json_table WHERE NAME = names);
END LOOP myloop;
END$
DELIMITER;
and I'm getting:
#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'BEGIN
DECLARE i INT;
DECLARE names VARCHAR(70);
SET i = 1;
Any help?
An example of a function which shows a major difference to your function:
CREATE FUNCTION `fnFindMaximum`(`a` INT, `b` INT)
/* Before the BEGIN statement there are other things going on - the most important being the return type statement */
RETURNS int(11)
LANGUAGE SQL
DETERMINISTIC
CONTAINS SQL
SQL SECURITY DEFINER
COMMENT ''
BEGIN
DECLARE returnval INTEGER;
IF a >= b THEN
SET returnval = a;
ELSE
SET returnval = b;
END IF;
RETURN returnval;
END
Your function then goes on to manipulate sql but does not return a value so, as was pointed out by #arkhil, use a StoredProcedure in preference to a function.
I am trying to assign the #lastupd variable. as in below line:
select #lastupd := max(`last_edited_time`)
from flyspray_comments where task_id = taskID;
But mysql give me error:
ERROR 1064 (42000): You have an error in your SQL syntax; check the
manual that corresponds to your MySQL server version for the right
syntax to use near 'BEGIN
set #lastupd = 0; select #lastupd := max(last_edited_time) from
flys' at line 2
The code:
delimiter $$
use flyspray $$
CREATE function last_upd_time(taskID INT)
BEGIN
set #lastupd = 0;
select #lastupd := max(`last_edited_time`) from flyspray_comments where task_id = taskID;
RETURN #lastupd;
END
$$
delimiter ;
Your immediate error has nothing to do with assignment. It is caused by the invalid definition of the function. You're missing mandatory RETURNS clause which indicates the return type of the function. See CREATE FUNCTION Syntax.
There is no need to use a variable in your case, less a user(session) variable. Just RETURN the result of the query.
And since you may use the only statement there is no need in a BEGIN ... END block and changing DELIMITER
That being said a streamlined and working version of your function may look like
CREATE FUNCTION last_upd_time(_task_id INT)
RETURNS DATETIME -- mandatory clause
RETURN -- just return the result of the query
(
SELECT MAX(last_edited_time)
FROM flyspray_comments
WHERE task_id = _task_id
); -- use default delimiter since it's a one-statement function
Here is SQLFiddle demo
Now, if you'd like to use a variable for some reason then
use a local instead of user(session) one.
assign a value with either SET or SELECT ... INTO syntax.
It may look like
DECLARE lastupd DATETIME DEFAULT NULL; -- or 0
SET lastupd =
(
SELECT MAX(last_edited_time)
FROM flyspray_comments
WHERE task_id = _task_id
);
or
DECLARE lastupd DATETIME DEFAULT NULL; -- 0
SELECT MAX(last_edited_time)
INTO lastupd
FROM flyspray_comments
WHERE task_id = _task_id;
I want to be able to pass an "array" of values to my stored procedure, instead of calling "Add value" procedure serially.
Can anyone suggest a way to do it? am I missing something here?
Edit: I will be using PostgreSQL / MySQL, I haven't decided yet.
As Chris pointed, in PostgreSQL it's no problem - any base type (like int, text) has it's own array subtype, and you can also create custom types including composite ones. For example:
CREATE TYPE test as (
n int4,
m int4
);
Now you can easily create array of test:
select ARRAY[
row(1,2)::test,
row(3,4)::test,
row(5,6)::test
];
You can write a function that will multiply n*m for each item in array, and return sum of products:
CREATE OR REPLACE FUNCTION test_test(IN work_array test[]) RETURNS INT4 as $$
DECLARE
i INT4;
result INT4 := 0;
BEGIN
FOR i IN SELECT generate_subscripts( work_array, 1 ) LOOP
result := result + work_array[i].n * work_array[i].m;
END LOOP;
RETURN result;
END;
$$ language plpgsql;
and run it:
# SELECT test_test(
ARRAY[
row(1, 2)::test,
row(3,4)::test,
row(5,6)::test
]
);
test_test
-----------
44
(1 row)
If you plan to use MySQL 5.1, it is not possible to pass in an array.
See the MySQL 5.1 faq
If you plan to use PostgreSQL, it is possible look here
I don't know about passing an actual array into those engines (I work with sqlserver) but here's an idea for passing a delimited string and parsing it in your sproc with this function.
CREATE FUNCTION [dbo].[Split]
(
#ItemList NVARCHAR(4000),
#delimiter CHAR(1)
)
RETURNS #IDTable TABLE (Item VARCHAR(50))
AS
BEGIN
DECLARE #tempItemList NVARCHAR(4000)
SET #tempItemList = #ItemList
DECLARE #i INT
DECLARE #Item NVARCHAR(4000)
SET #tempItemList = REPLACE (#tempItemList, ' ', '')
SET #i = CHARINDEX(#delimiter, #tempItemList)
WHILE (LEN(#tempItemList) > 0)
BEGIN
IF #i = 0
SET #Item = #tempItemList
ELSE
SET #Item = LEFT(#tempItemList, #i - 1)
INSERT INTO #IDTable(Item) VALUES(#Item)
IF #i = 0
SET #tempItemList = ''
ELSE
SET #tempItemList = RIGHT(#tempItemList, LEN(#tempItemList) - #i)
SET #i = CHARINDEX(#delimiter, #tempItemList)
END
RETURN
END
You didn't indicate, but if you are referring to SQL server, here's one way.
And the MS support ref.
For PostgreSQL, you could do something like this:
CREATE OR REPLACE FUNCTION fnExplode(in_array anyarray) RETURNS SETOF ANYELEMENT AS
$$
SELECT ($1)[s] FROM generate_series(1,array_upper($1, 1)) AS s;
$$
LANGUAGE SQL IMMUTABLE;
Then, you could pass a delimited string to your stored procedure.
Say, param1 was an input param containing '1|2|3|4|5'
The statement:
SELECT CAST(fnExplode(string_to_array(param1, '|')) AS INTEGER);
results in a result set that can be joined or inserted.
Likewise, for MySQL, you could do something like this:
DELIMITER $$
CREATE PROCEDURE `spTest_Array`
(
v_id_arr TEXT
)
BEGIN
DECLARE v_cur_position INT;
DECLARE v_remainder TEXT;
DECLARE v_cur_string VARCHAR(255);
CREATE TEMPORARY TABLE tmp_test
(
id INT
) ENGINE=MEMORY;
SET v_remainder = v_id_arr;
SET v_cur_position = 1;
WHILE CHAR_LENGTH(v_remainder) > 0 AND v_cur_position > 0 DO
SET v_cur_position = INSTR(v_remainder, '|');
IF v_cur_position = 0 THEN
SET v_cur_string = v_remainder;
ELSE
SET v_cur_string = LEFT(v_remainder, v_cur_position - 1);
END IF;
IF TRIM(v_cur_string) != '' THEN
INSERT INTO tmp_test
(id)
VALUES
(v_cur_string);
END IF;
SET v_remainder = SUBSTRING(v_remainder, v_cur_position + 1);
END WHILE;
SELECT
id
FROM
tmp_test;
DROP TEMPORARY TABLE tmp_test;
END
$$
Then simply CALL spTest_Array('1|2|3|4|5') should produce the same result set as the above PostgreSQL query.
Thanks to JSON support in MySQL you now actually have the ability to pass an array to your MySQL stored procedure. Create a JSON_ARRAY and simply pass it as a JSON argument to your stored procedure.
Then in procedure, using MySQL's WHILE loop and MySQL's JSON "pathing" , access each of the elements in the JSON_ARRAY and do as you wish.
An example here https://gist.githubusercontent.com/jonathanvx/513066eea8cb5919b648b2453db47890/raw/22f33fdf64a2f292688edbc67392ba2ccf8da47c/json.sql
Incidently, here is how you would add the array to a function (stored-proc) call:
CallableStatement proc = null;
List<Integer> faultcd_array = Arrays.asList(1003, 1234, 5678);
//conn - your connection manager
conn = DriverManager.getConnection(connection string here);
proc = conn.prepareCall("{ ? = call procedureName(?) }");
proc.registerOutParameter(1, Types.OTHER);
//This sets-up the array
Integer[] dataFaults = faultcd_array.toArray(new Integer[faultcd_array.size()]);
java.sql.Array sqlFaultsArray = conn.createArrayOf("int4", dataFaults);
proc.setArray(2, sqlFaultsArray);
//:
//add code to retrieve cursor, use the data.
//: