I have the following code attempting to truncate a table. The Joomla documentation makes me believe this will work, but it does not. What am I missing?
$db = JFactory::getDbo();
truncate_query = $db->getQuery(true);
//$truncate_query = 'TRUNCATE ' . $db->quoteName('#__mytable');
$truncate_query->truncateTable($db->quoteName('#__mytable'));
$db->setQuery($truncate_query);
echo $truncate_query;
exit();
If I use the line that is commented out to manually generate the SQL, it does work. The reason I am still looking to use the truncateTable function is that I am trying to include the truncation in a transaction. When I use the manual statement, the table is still truncated even if another part of the transaction fails, which is annoying since the other statements rely on data that is truncated, so if the table is emptied when it shouldn't be there is no data left to run the transaction again. Very annoying!
Here's how you call/execute your truncation query:
JFactory::getDbo()->truncateTable('#__mytable');
And now some more details...
Here is the method's code block in the Joomla source code:
public function truncateTable($table)
{
$this->setQuery('TRUNCATE TABLE ' . $this->quoteName($table));
$this->execute();
}
As you can see the truncateTable() method expects a tablename as a string for its sole parameter; you are offering a backtick-wrapped string -- but the method already offers the backtick-wrapping service. (Even if you strip your backticks off, your approach will not be successful.)
The setQuery() and execute() calls are already inside the method, so you don't need to create a new query object nor execute anything manually.
There is no return in the method, so the default null is returned -- ergo, your $truncate_query becomes null. When you try to execute(null), you get nothing -- not even an error message.
If you want to know how many rows were removed, you will need to run a SELECT query before hand to count the rows.
If you want to be sure that there are no remaining rows of data, you'll need to call a SELECT and check for zero rows of data.
Here is my answer (with different wording) on your JSX question.
I'm trying to perform a check to see if a record exist first before inserting the record so I won't get an error.
If it exists, i'll update a field.
mydb(mydb.myitems.itemNumber==int(row)).update(oldImageName=fileName) or
mydb.myitems.insert(itemNumber=int(row),oldImageName=fileName)
If i try to update a record that does not exist, then it should throw a 1 or something aside from 0. But in the case above, it always throws a 0 so the insert keeps happening.
Why is that?
Thanks!
UPDATE:
Adding model:
mydb.define_table('myitems',
Field('itemNumber', 'id',notnull=True,unique=True),
Field('oldImageName', 'string')
If i try to update a record that does not exist, then it should throw a 1 or something aside from 0.
If you try to update a record that does not exist, .update() will return None, so the insert will then happen. If matching records exist, .update() will return the number of records updated.
In any case, you should instead do:
mydb.myitems.update_or_insert(mydb.myitems.itemNumber == int(row),
oldImageName=filename)
or alternatively:
mydb.myitems.update_or_insert(dict(itemNumber == int(row)),
oldImageName=filename)
The first argument to update_or_insert is _key, which can either be a DAL query or a dictionary with field names as keys.
This is basically a correction of Anthony's answer which did not give quite the desired result when I tried it. If you do:
mydb.myitems.update_or_insert(mydb.myitems.itemNumber == int(row),
itemNumber = int(row),
oldImageName=filename)
then the code should insert a record with the itemNumber and filename if there is not an item with that number there already, otherwise update it.
If you miss the itemNumber = int(row), bit then web2py makes up an itemNumber which is probably not what is wanted.
See http://www.web2py.com/books/default/chapter/29/06/the-database-abstraction-layer#update_or_insert
I'm doing an update query with PDO. I would like to figure out if my update query did not change anything in the database, since:
the passed values are the same as already present in the database. I know that rowCount() in such a case returns 0.
the row I'm trying to update does not exist in the database. As far as I can see, rowCount()in such cases also returns 0.
Am I forced to precede my UPDATE by a SELECT statement, to figure out if the record I'm trying to update does in fact exist? Or is there another common practice for this sort of thing.
I've been perusing through the documentation, but cannot find a conclusive answer:
http://php.net/manual/en/pdostatement.rowcount.php
I've come across this StackOverflow answer, that suggests that rowCount() might return NULL in some scenario's, but I don't think it's apliccable to my scenario:
see Why does PDO rowCount() return 0 after UPDATE a table without modifying the existing data?
From the comments in this question:
If the data hasn't been modified, the rowCount will be zero. If the
data was modified, the rowCount will be one or higher. If there was an
error, rowCount will be null or false or something non-zero.
UPDATE
I've found another question that gives an example of the proposition in the comments below:
Getting the insert and update ID with PDO
UPDATE2
Another question proposes another solution, via PDO::MYSQL_ATTR_FOUND_ROWS
PDO - check if row was updated?
You could add conditionals to your 'where' clause so such as " and ColumnToUpdate <> 'NewValue'"
I've solved it using the suggestions of #hjpotter92.
// UID is the unique ID of my table, autoincremented etc...
// Firstly, let's try to update my row
$query = 'UPDATE my_table SET x=0, y=1, uid=LAST_INSERT_ID(uid) WHERE z=2';
$sth = $dbh->prepare($query);
if($sth->execute()) {
if($dbh->lastInsertId() == 0) { // Record was not found, so insert it.
$query = 'INSERT INTO my_table (x,y) VALUES (0,1)';
$sth = $dbh->prepare($query);
$sth->execute();
if($sth->rowCount() > 0) {
echo $dbh->lastInsertId(); // Return the UID of the inserted row
}
}
}
I am using DBIx::Class and I would like to only update one row in my table. Currently this is how I do it:
my $session = my_app->model("DB::Session")->find(1);
$session->update({done_yn=>'y',end_time=>\'NOW()'});
It works, but the problem is that when it does find to find the row, it does this whole query:
SELECT me.id, me.project_id, me.user_id, me.start_time, me.end_time, me.notes, me.done_yn FROM sessions me WHERE ( me.id = ? ): '8'
Which seems a bit much when all I want to do is update a row. Is there anyway to update a row without having to pull the whole row out of the database first? Something like this is what I am looking for:
my_app->model("DB::Session")->update({done_yn=>'y',end_time=>\'NOW()'},{id=>$id});
Where $id is the WHERE id=? part of the query. Does anyone know how to do this? Thanks!
You can run update on a restricted resultset which only matches this single row:
my_app->model("DB::Session")->search_rs({ id=> 1 })->update({done_yn=>'y',end_time=>\'NOW()'});
I suggest you use a DateTime->now object instead of literal SQL for updating the end_time column because it uses the apps servers date and time instead of the database servers and makes your schema more compatible with different RDBMSes.
Do you have a check if the row was found to prevent an error in case it wasn't?
You might want to use update_or_create instead.
You could use the "columns" attribute:
my $session = my_app->model("DB::Session")->find(1, {columns => "id"});
I'm trying to update the column visited to give it the value 1. I use MySQL workbench, and I'm writing the statement in the SQL editor from inside the workbench. I'm writing the following command:
UPDATE tablename SET columnname=1;
It gives me the following error:
You are using safe update mode and you tried to update a table without
a WHERE that uses a KEY column To disable safe mode, toggle the option
....
I followed the instructions, and I unchecked the safe update option from the Edit menu then Preferences then SQL Editor. The same error still appear & I'm not able to update this value. Please, tell me what is wrong?
It looks like your MySql session has the safe-updates option set. This means that you can't update or delete records without specifying a key (ex. primary key) in the where clause.
Try:
SET SQL_SAFE_UPDATES = 0;
Or you can modify your query to follow the rule (use primary key in where clause).
Follow the following steps before executing the UPDATE command:
In MySQL Workbench
Go to Edit --> Preferences
Click "SQL Editor" tab and uncheck "Safe Updates" check box
Query --> Reconnect to Server // logout and then login
Now execute your SQL query
p.s., No need to restart the MySQL daemon!
SET SQL_SAFE_UPDATES = 0;
# your code SQL here
SET SQL_SAFE_UPDATES = 1;
SET SQL_SAFE_UPDATES=0;
UPDATE tablename SET columnname=1;
SET SQL_SAFE_UPDATES=1;
No need to set SQL_SAFE_UPDATES to 0, I would really discourage it to do it that way. SAFE_UPDATES is by default on for a REASON. You can drive a car without safety belts and other things if you know what I mean ;)
Just add in the WHERE clause a KEY-value that matches everything like a primary-key comparing to 0, so instead of writing:
UPDATE customers SET countryCode = 'USA'
WHERE country = 'USA'; -- which gives the error, you just write:
UPDATE customers SET countryCode = 'USA'
WHERE (country = 'USA' AND customerNumber <> 0); -- Because customerNumber is a primary key you got no error 1175 any more.
Now you can be assured every record is (ALWAYS) updated as you expect.
Error Code: 1175. You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column To disable safe mode, toggle the option in Preferences -> SQL Editor and reconnect.
Turn OFF "Safe Update Mode" temporary
SET SQL_SAFE_UPDATES = 0;
UPDATE options SET title= 'kiemvieclam24h' WHERE url = 'http://kiemvieclam24h.net';
SET SQL_SAFE_UPDATES = 1;
Turn OFF "Safe Update Mode" forever
Mysql workbench 8.0:
MySQL Workbench => [ Edit ] => [ Preferences ] -> [ SQL Editor ] -> Uncheck "Safe Updates"
Old version can:
MySQL Workbench => [Edit] => [Preferences] => [SQL Queries]
Preferences...
"Safe Updates"...
Restart server
SET SQL_SAFE_UPDATES=0;
OR
Go to Edit --> Preferences
Click SQL Queries tab and uncheck Safe Updates check box
Query --> Reconnect to Server
Now execute your sql query
If you are in a safe mode, you need to provide id in where clause. So something like this should work!
UPDATE tablename SET columnname=1 where id>0
On WorkBench I resolved it By deactivating the safe update mode:
-Edit -> Preferences -> Sql Editor then uncheck Safe update.
The simplest solution is to define the row limit and execute. This is done for safety purposes.
I found the answer. The problem was that I have to precede the table name with the schema name. i.e, the command should be:
UPDATE schemaname.tablename SET columnname=1;
Thanks all.
In the MySQL Workbech version 6.2 don't exits the PreferenceSQLQueriesoptions.
In this case it's possible use: SET SQL_SAFE_UPDATES=0;
Since the question was answered and had nothing to do with safe updates, this might be the wrong place; I'll post just to add information.
I tried to be a good citizen and modified the query to use a temp table of ids that would get updated:
create temporary table ids ( id int )
select id from prime_table where condition = true;
update prime_table set field1 = '' where id in (select id from ids);
Failure. Modified the update to:
update prime_table set field1 = '' where id <> 0 and id in (select id from ids);
That worked. Well golly -- if I am always adding where key <> 0 to get around the safe update check, or even set SQL_SAFE_UPDATE=0, then I've lost the 'check' on my query. I might as well just turn off the option permanently. I suppose it makes deleting and updating a two step process instead of one.. but if you type fast enough and stop thinking about the key being special but rather as just a nuisance..
I too got the same issue but when I off 'safe updates' in Edit ->
Preferences -> SQL Editor -> Safe Updates, still I use to face the
error as "Error code 1175 disable safe mode"
My solution for this error is just given the primary key to the table if not given and update the column using those primary key value.
Eg: UPDATE [table name] SET Empty_Column = 'Value' WHERE
[primary key column name] = value;
True, this is pointless for the most examples. But finally, I came to the following statement and it works fine:
update tablename set column1 = '' where tablename .id = (select id from tablename2 where tablename2.column2 = 'xyz');
This is for Mac, but must be same for other OS except the location of the preferences.
The error we get when we try an unsafe DELETE operation
On the new window, uncheck the option Safe updates
Then close and reopen the connection. No need to restart the service.
Now we are going to try the DELETE again with successful results.
So what is all about this safe updates? It is not an evil thing. This is what MySql says about it.
Using the --safe-updates Option
For beginners, a useful startup option is --safe-updates (or
--i-am-a-dummy, which has the same effect). It is helpful for cases when you might have issued a DELETE FROM tbl_name statement but
forgotten the WHERE clause. Normally, such a statement deletes all
rows from the table. With --safe-updates, you can delete rows only by
specifying the key values that identify them. This helps prevent
accidents.
When you use the --safe-updates option, mysql issues the following
statement when it connects to the MySQL server:
SET sql_safe_updates=1, sql_select_limit=1000, sql_max_join_size=1000000;
It is safe to turn on this option while you deal with production database. Otherwise, you must be very careful not accidentally deleting important data.
just type SET SQL_SAFE_UPDATES = 0; before the delete or update and set to 1 again
SET SQL_SAFE_UPDATES = 1
If you're having this problem in a stored procedure and you aren't able to use the key in the WHERE clause, you can solve this by declaring a variable that will hold the limit of the rows that should be updated and then use it in the update/delete query.
DELIMITER $
CREATE PROCEDURE myProcedure()
BEGIN
DECLARE the_limit INT;
SELECT COUNT(*) INTO the_limit
FROM my_table
WHERE my_column IS NULL;
UPDATE my_table
SET my_column = true
WHERE my_column IS NULL
LIMIT the_limit;
END$
As stated in previous posts, changing the default settings of the database server will result in undesired modification of existing data due to an incorrect query on the data in a published project. Therefore, to implement such commands as stated in previous posts, it is necessary to run them in a test environment on sample data and then execute them after testing them correctly.
My suggestion is to write a WHERE conditional statement that will loop through all the rows in all conditions if an update should work for all rows in a table. For example, if the table contains an ID value, the condition ID > 0 can be used to select all rows:
/**
* For successful result, "id" column must be "Not Null (NN)" and defined in
* INT data type. In addition, the "id" column in the table must have PK, UQ
* and AI attributes.
*/
UPDATE schema_name.table_name
SET first_column_name = first_value, second_column_name = second_value, ...
WHERE id > 0;
If the table does not contain an id column, the update operation can be run on all rows by checking a column that cannot be null:
/**
* "first_column_name" column must be "Not Null (NN)" for successful result.
*/
UPDATE schema_name.table_name
SET first_column_name = first_value, second_column_name = second_value, ...
WHERE table_name.first_column_name IS NOT NULL;
MySql workbench gave me the same error, after I unchecked safe mode , I then reconnected the server and the update function worked.
Go to Query in the menu bar and reconnect the server
Query Menu -> Reconnect to Server
You can enable and disable safe update option by following commands.
To Disable,
SET SQL_SAFE_UPDATES=0;
or
SET SQL_SAFE_UPDATES=OFF;
To Enable,
SET SQL_SAFE_UPDATES=1;
or
SET SQL_SAFE_UPDATES=ON;
First:
Please make sure you want to update all records in that table because without the where clause it is dangerous to update all records in that table. It's rare time you want to update all records in the table.
most of the time you want to update specific records which should include where cluase if again you want to update all records open MySQL workbench> Edit> Preference>SQL Editor > scroll down at right and uncheck the "Safe Updates(rejects UPDATEs and DELETEs with no restrictions)".
It is for safe updates.
If you uncheck the above said then there are chances that you update all records instead of one record which leads to a database backup restore. there is no rollback.
I've just added COMMIT; in the end
You can enable and disable safe update option by following commands.
SET SQL_SAFE_UPDATES=1;