I am a newbie to using query strings in mysql and I have tried to write this procedure to drop tables under certain conditions. I don't reall know what I'm doing wrong and need help with getting the procedure to work or for someone to point me in the right direction. Thanks.
BEGIN
DECLARE String scheduler = 'select status from mysql.scheduler where id=0' ;
DECLARE String auftragpos = 'SELECT count("SchemaName") FROM "SYS.Tables" where "SchemaName" = dwh and "Name" = lexware_fk_auftragpos';
DECLARE String auftrag = 'SELECT count("SchemaName") FROM "SYS.Tables" where "SchemaName" = dwh and "Name" = lexware_fk_auftrag';
IF(auftragpos > 1)
BEGIN
drop table "dwh.lexware_fk_auftragpos";
END
IF(auftrag > 1)
BEGIN
drop table "dwh.lexware_fk_auftrag";
END
END
The syntax for declaring a variable is
DECLARE variablename datatype;
So it should be
DECLARE auftragpos INT;
Then you need to assign the result of the query to the variable. You do that by putting the SELECT query in parentheses.
You also should not quote table names, and you need to quote the literal strings you're using for the schema and table names you're searching for.
SET auftragpos = (
SELECT count(*)
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA = 'dwh' AND TABLE_NAME = 'lexware_fk_auftragpos');
But there's really no need to do this. If you want to prevent an error from DROP TABLE, just add the IF EXISTS option.
DROP TABLE IF EXISTS dwh.lexware_fk_auftragpos;
I wanted to SET a value into a VARCHAR but I don't understand how to combine it.
DECLARE id INTEGER;
DECLAR action VARCHAR(100);
SET id = (SELECT MAX(ID) FROM Test.Test);
SET action = "This is a test" + id;
Somehow I am losing the textpart "This is a test".
Is this normal behaviour for MySQL, am I doing something wrong ?
You can use MySQL functions.
SET action = CONCAT('This is a test',id);
In the code below, I'm trying go through the results of endDateTable row by row, comparing the current row's endDate to the previous row's endDate. If there has been any change since the previous, we increment #revisionNum. However, upon populating the new table, all of the #revisionNum entries are 0. What am I doing wrong?
NOTE: I'm using prepared statements in this manner since doing a straightforward SELECT into a variable gives a syntax error due to the LIMIT clause not allowing a variable in our version of MySQL.
BEGIN
DECLARE _currentEndDate DATETIME DEFAULT now();
DECLARE _priorEndDate DATETIME DEFAULT now();
SET #ResultsCount = (SELECT COUNT(*) FROM mainTable);
SET #j = 0;
WHILE #j < #ResultsCount DO
SET #revisionNum = 0;
/*CURRENT END DATE*/
SET #appResultQueryCurrent = CONCAT('
SELECT
end_date
INTO _currentEndDate
FROM endDateTable
LIMIT ', #j, ', 1'
);
PREPARE currentQueryStmt FROM #appResultQueryCurrent;
EXECUTE currentQueryStmt;
/*PREVIOUS END DATE*/
SET #appResultQueryPrior = CONCAT('
SELECT
end_date
INTO _priorAppEndDate
FROM endDateTable
LIMIT ', IF(#j = 0, 0, #j - 1), ', 1'
);
PREPARE priorQueryStmt FROM #appResultQueryPrior;
EXECUTE priorQueryStmt;
SET #revisionNum = IF(
#j = 0 OR (_currentEndDate = _priorEndDate),
#revisionNum,
IF(
_currentEndDate != _priorEndDate,
#revisionNum + 1,
#revisionNum
)
);
INSERT INTO finalTable (RevisionNum)
SELECT
#revisionNum AS RevisionNum
FROM endDateTable;
SET #j = #j +1;
END WHILE;
END $$
You don't need a loop, you can use INSERT INTO ... SELECT ..., incrementing the variable in the select query.
You also need an ORDER BY criteria to specify how to order the rows when comparing one row to the previous row.
INSERT INTO finalTable (RevisionNum, otherColumn)
SELECT revision, otherColumn
FROM (
SELECT IF(end_date = #prev_end_date, #revision, #revision := #revision + 1) AS revision,
#prev_end_date := end_date,
otherColumn
FROM endDateTable
CROSS JOIN (SELECT #prev_end_date := NULL, #revision := -1) AS vars
ORDER BY id) AS x
DEMO
The offset value in the LIMIT clause is tenuous without an ORDER BY.
Without an ORDER BY clause, MySQL is free to return results in any sequence.
There is no guarantee that LIMIT 41,1 will return the row before LIMIT 42,1, or that it won't return the exact same row as LIMIT 13,1 did.
(A table in a relational database represents an unordered set of tuples, there is no guaranteed "order" or rows in a table.)
But just adding ORDER BY to the queries isn't enough to fix the Rube-Goldberg-esque rigmarole.
In the code shown, it looks like each time through the loop, we're inserting a copy of endDateTable into finalTable. If that's 1,000 rows in endDateTable, we're going to get 1,000,000 rows (1,000 x 1,000) inserted into finalTable. Not at all clear why we need so many copies.
Given the code shown, it's not clear what the objective is. Looks like we are conditionally incrementing revisionNum, the end result of which is the highest revision num. Just guessing here.
If there is some kind of requirement to do this in a LOOP construct, within a procedure, I'd think we'd do a cursor loop. And we can use procedure variables vs user-defined variables.
Something along these lines:
BEGIN
DECLARE ld_current_end_date DATETIME;
DECLARE ld_prior_end_date DATETIME;
DECLARE li_done INT;
DECLARE li_revision_num INT;
DECLARE lcsr_end_date CURSOR FOR SELECT t.end_date FROM `endDateTable` t ORDER BY NULL;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET li_done = TRUE;
SET li_done = FALSE;
SET li_revision_num = 0;
OPEN lcsr_end_date;
FETCH lcsr_end_date INTO ld_current_end_date;
SET ld_prior_end_date = ld_current_end_date;
WHILE NOT li_done DO
SET li_revision_num = li_revision_num + IF( ld_current_end_date <=> ld_prior_end_date ,0,1);
SET ld_prior_end_date := ld_current_end_date;
FETCH lcsr_end_date INTO ld_current_end_date;
END WHILE;
CLOSE lcsr_end_date;
INSERT INTO `finalTable` (revisionnum) VALUES (li_revision_num);
END $$
Note the "order by" clause on the SELECT, its not clear what the rows should be ordered on, so we're using a literal as a placeholder.
As the end result, we insert a single row into finalTable.
Again, it's not clear what the code in the question is supposed to achieve, but doing a cursor loop across ordered rows would be much more efficient than a bazillion dynamic SQL executions fetching individual rows.
Stored Proc Definition:
DECLARE dbName varchar(255);
DECLARE tableName varchar(255);
DECLARE fullPath varchar(255);
DECLARE conditions varchar(255);
SET dbName = idbname;
SET tableName = itablename;
SET fullPath = CONCAT("'",dbName,"'",'.',"'",tableName,"'");
SET checkExists = 0;
I am creating a stored proc where the dbname and tablename are dynamic, however I am stuck on the select aspect of this query.
I am trying to repalce the _test.user with values passed into the stored proc.
SELECT count(*) INTO checkExists FROM `_test`.`user` WHERE id = 1;
However this line throws an error
SELECT count(*) INTO checkExists FROM fullPath WHERE id = 1;
Error:
Procedure execution failed
1146 - Table 'dbname.fullpath' doesn't exist
I have also tried CONCAT() like this
set conditions = CONCAT('SELECT count(*) INTO ',checkExists, ' FROM ', fullPath, ' WHERE id=', 1);
However I can't figure out even how to use this in a select? Help is appreciated.
I like to do these modifications using replace(). Something like this:
replace(replace('SELECT count(*) INTO checkExists FROM `<dbname>`.`<tname>` WHERE id = 1',
'<tname>', v_tablename
), '<dbname>', v_databasename
)
You may also want to use v_fullpath somewhere. I'm not really sure what query you actually want to create.
I'm not sure why you have a variable called checkExists, when it seems to be the destination file. However, I would suggest that you prepend all your local variables with something to distinguish them from column names.
Here,when I am passing correct and incorrect value,both the times I am getting result as 4
When I am executing this query
select Count(*) into result
from document_details
where document_name = name
and document_path = path;
then it shows me correct answer which is 1.
Kindly help me ASAP. Thank You in advance!!
create procedure check_status(IN name INT(30),IN path INT(255))
BEGIN
declare result int;
set result = 0;
select Count(*) into result from `document_details` where `document_name`=name and `document_path`=path;
select result;
END
IF types are OK, then that shoud work id not, change then into i.e. (name CHAR(30),path CHAR(255))
create procedure check_status(name INT(30),path INT(255))
BEGIN
select Count(*) as result from `document_details`
where `document_name`=name and `document_path`=path;
END;
In procedures there is no IN/OUT in funcions there are...