I am running an update query using PDO. I am updating only four rows but I do not know the names of columns. I can easily get the count of rows using rowCount() but I also want to fetch the column name as well. Is there any function in PDO which will help for the same? If not then please tell me the other method for fetching this.
You don't need PDO, you can get the names with MySQL:
SHOW COLUMNS FROM `table`
Hope it helps
Related
I'm a beginner with PDO and MySQL, so here's my question :
How can I be sure that when performing an INSERT .. SELECT (or MULTIPLE INSERT)
all data will be inserted in database?
I know there is a rowCount() function but the number of rows inserted is dynamic.
The only way I see would be to make a SELECT count(*), and then compare it with the rowCount(), but I'm not sure I'm doing it the right way.
And if not all data were inserted, is it possible to get rows which didn't work?
Also, is it possible that a SELECT query fails and retrieves only a few part of the data? (ex : It must retrieve 1000 rows but due to some failure, it retrieves 700) Or it's all or nothing?
Thanks for the help.
How can I be sure that when performing an INSERT .. SELECT (or MULTIPLE INSERT) all data will be inserted in database?
You should tell PDO to throw an exception in case of error and thus there will be a PHP error in case of a failed query.
I know there is a rowCount() function
Row count has nothing to do in your case.
And if not all data were inserted, is it possible to get rows which didn't work?
It is advised to redo all the successful yet queries instead. To do so you have to wrap your inserts in a transaction.
However, if you want to keep alll the previous inserts in place, you may wrap execute call in a try and catch operator and do whatever workaround inside.
Also, is it possible that a SELECT query fails and retrieves only a few part of the data?
No.
Until recently I've been using mysql_real_escape_string() to fix most of my variables before making SQL queries to my database. A friend said that I should be using PDO's prepared statements instead, so after reading a bit about them I'm now switching over to them.
I've only encountered one problem so far in switching over, and that's counting the rows to returned by a SELECT statement. On occasion in my code, I'd run an SQL query and then count the number of rows returned from the SELECT statement. Depending on whether a result set returned, I would take different actions. Sometimes I do need to use the result set from it. MySQL let me go straight to mysql_fetch_assoc() after mysql_num_rows() with no problem. However, PDO doesn't seem to have anything like mysql_num_rows().
I've been reading some responses on SO that gave me a solution, to either use COUNT() in the SQL statement or to use the PHP function count() on the result set. COUNT() would work fine in the SQL statement if I didn't need the result set in some places, however, several people have mentioned that using count() on the result set is fairly inefficient.
So my question is, how should I be doing this if I need to count the number of rows selected (if any), then run a script with the result set? Is using count() on the result set the only way in this case, or is there a more efficient way to do things?
Below is a short example of something similar to my previous SQL code:
$query=mysql_query('SELECT ID FROM Table WHERE Name='Paul' LIMIT 1);
if(mysql_num_rows($query)>0)
{
print_r(mysql_fetch_assoc($query));
}
else
{
//Other code.
}
Thanks.
EDIT
I do know that you use fetchAll() on the statement before counting the result set (which gives me what I need), but I'm just trying to figure out the most efficient way to do things.
$stmt->rowCount();
http://php.net/manual/en/pdostatement.rowcount.php
the rows must be fetched(buffered into memory, or iterated) for it to work. It's not uncommon for your pdo driver to be configured to do this automatically.
You will have to use Count(). You can run two queries like
SELECT COUNT(ID) FROM Table WHERE Name='Paul'
one you have get the count, then run the query with select clause
SELECT ID FROM Table WHERE Name='Paul' LIMIT 1
Count() function is not inefficient at all if you are using it like COUNT(ID), because most probably id is primary key and have an index. MYSQL wont even have to access the table.
In php, I'm trying to insert a value into one table, return an auto-incremented value, and then insert that value along with other values into a second table.
I'm running into a few problems. First, while there's a lot of ways of doing this in SQL, I have to do this with php's mysql functions. I'm afraid of weird errors if I combine multiple statements together. Second, like I mentioned, I need this to be done in one query, as it'll be used for a web application.
My current query is like this
INSERT INTO TABLE1 VALUES(*);
INSERT INTO TABLE2
SELECT max(AutoIncrementedColumn)
FROM TABLE1;
The problem I'm having is that mysql_query() doesn't support multi queries. Also, I believe mysql_escape_string() removes anything it believes to be a multi query, so even if I could somehow get mysql_query to believe my query is not a multi query, I'm still out of luck unless I write my own escape method.
Does anyone have any ideas on how to deal with this problem?
EDIT: Forgot to mention that I can't use mysql_insert_id because the column that's autoincrementing is of type Bigint.
In php I have an INSERT query to database. This query add some issue to database. I want to check if issue was added fine (there are some cases when issue doesn't added - without any mistake reporting). How to check this?
I have an idea, that after i make INSERT query i should make a query, for example: SELECT ..... WHERE id=last_id. But how to get the last_id - how to get id of last INSERT query? (id is autoincrementing sql field)
Thank you
mysql_insert_id();
You may find the answer to this StackOverflow question useful:
SQL - INSERT and catch the id auto-increment value
mysql_insert_id()
More info at http://php.net/manual/en/function.mysql-insert-id.php and http://dev.mysql.com/doc/refman/5.0/en/getting-unique-id.html
mysql_insert_id function returns id of previously inserted record.
I assume you're working with MySQL
I've recently started work on a new project using PHP5 and want to use their PDO classes for it. The problem is that the MySQL PDO Driver doesn't support rowCount() so there's no way to run a query and then get the number of affected rows, or rows returned, which is a pretty big issue as far as I'm concerned. I was wondering if anyone else has dealt with this before and what you've done to work around it. Having to do a fetch() or fetchAll() to check if any rows were affected or returned seems like a hack to me, I'd rather just do $stmt->numRows() or something similar.
You can issue a SELECT FOUND_ROWS() query right after the original SELECT query to get row count.
$pdo->query("SELECT * FROM users");
$foundRows = $pdo->query("SELECT FOUND_ROWS()")->fetchColumn();
See also: MySQL Docs on FOUND_ROWS()
For those of you who are using MySQL stored procedures, this solution isn't really feasible. What I would suggest that you do is have your stored procedure create two rowsets. The first one will contain one row and one column, containing the number of records. The second will be the recordset you will use for fetching that number of rows.
The number of unlimited rows can be a SELECT COUNT(*) with the exact same WHERE clause as the second rowset without the LIMIT/OFFSET clauses.
Another idea could be to create a temporary table. Use your SELECT statement to populate the temporary table. Then you can use SELECT COUNT(*) FROM tmpTable for your first rowset and SELECT * FROM tmpTable for your second.
This question is based on several false assumptions and one outdated statement.
First of all, do not confuse number of affected and selected rows. PDO supported the former even back in '09.
Speaking of number of rows returned by SELECT statement - you just don't need that number. The data you have is enough.
And yeah, nowadays rowCount() supports number of rows selected from mysql as well. But again - you don't need that number in an average web-application anyway.