I want to count how many rows I have in a mysql table and display it in html.
For example:
There is: Item 1, Item 2, Item 3, Item 4, Item 5, Item 6
If Item 1 and Item 2 are filled, I want a html code to say - 2 items in row
any ideas?
you can use simple
Select count(*) from table
or If you want not null values
Select count(item) from table
IF its total rows you are after, then as Nishant mentioned above you could do something like this
$query = "SELECT COUNT(*) FROM mytable WHERE myfield='myvalue'";
I am counting all the ids, because it will reduce the time taken to calculate the total instead of '*' and
Thanks to Nico, count(*) and count(column) are not so different considering performance. Here is a comparision
Use a where condition to narrow your total as you require.
If you want to count only rows which are filled (meaning, which are not null), you should add a small WHERE clause, or specify the column of interest in the count() function:
using where
SELECT count(*) FROM mytable WHERE fieldx IS NOT NULL
specifying the field of interest
SELECT count(fieldx) FROM mytable
in this last solution, count() will only take into account not-null fieldx values.
You can get the number of rows of your query using the function mysql_num_rows().
So if you have a SELECT statement (to select which items you want), you just have to call mysql_num_rows() after doing the query. Example from php.net:
$link = mysql_connect("localhost", "mysql_user", "mysql_password");
mysql_select_db("database", $link);
$result = mysql_query("SELECT * FROM table1", $link);
$num_rows = mysql_num_rows($result);
echo "$num_rows Rows\n";
What do you mean by filled? Anyway, if by 'filled' you mean that some specific field has a NOT NULL value you could do something like this:
$sqlConn = new mysqli('host', 'user', 'password', 'database');
$sqlConn->query('SELECT * FROM table WHERE field1 IS NOT NULL AND field2 IS NOT NULL');
echo 'You have ' . $sqlConn->affected_rows . ' rows.';
Hope it helps.
Related
When I want to find out how many shoes Alfred has, I always count the rows in the table "usershoes" where the userid matches Alfred's
But since I switched to PDO, and select row count is not simple or bulletproof/consistent, I'm reconsidering my methods
Maybe I should instead keep an int field "shoes" directly in table "users", keep number of shoes there, and then increase/decrease that number for that user along the way? Feels not right..
If anyone has a solid method for simple row counting on an existing select query, without extra query, let me know
Try something like this
SELECT COUNT(*) FROM usershoes
WHERE userid="theIdOfTheUser";
I could not get count(fetchColumn()) or fetchColumn() to work correctly (outputted 1 when 0 was the real number)
So now I'm using this, and it works:
$sql = 'SELECT COUNT(*) as numrows, shoecolor FROM usershoes WHERE userid = ?'
$STH = $conn->prepare($sql);
$STH->execute(array($someuseridvar));
And then:
$row = $STH->fetch();
if ($row['numrows'] > 0) {
// at least one row was found, do something
}
With MySQL, you can use FOUND_ROWS():
$db = new PDO(DSN...);
$db->setAttribute(array(PDO::MYSQL_USE_BUFFERED_QUERY=>TRUE));
$rs = $db->query('SELECT SQL_CALC_FOUND_ROWS * FROM table LIMIT 5,15');
$rs1 = $db->query('SELECT FOUND_ROWS()');
$rowCount = (int) $rs1->fetchColumn();
$rowCount will contain the total number of rows, not 15.
Taken from:
http://php.net/manual/en/pdostatement.rowcount.php#83586
I can not find a proper answer to this question. I have a very simple code for making a query in mysql to select the row with the maximum value in a determined column (called popularity) from a table (called comments). Every row has a column named comment_id
here is the code:
$connect_error = 'Sorry, try again, there was a connection error';
$con = mysqli_connect('localhost','user_name','password') or die($connect_error);
mysqli_select_db($con, 'database') or die($connect_error);
$result = mysqli_query($con, "SELECT MAX(`popularity`) FROM `comments`");
while ($row = mysqli_fetch_assoc($result)) {
$most_popular = $row['comment_id'];
}
echo "most popular is: $most_popular";
mysqli_free_result($result);
mysqli_close($con);
the screen does not show a proper result. Can someone give me an advice in this regard?
Thank you
You are looking to display the comment_id field, but you don't have that in your SELECT query. You are only selecting the max popularity value, and nothing else.
Try this for your query:
SELECT comment_id FROM comments ORDER BY popularity DESC LIMIT 1
This is sorting your comments by popularity, and then just picking the top one.
Of course you can easily change that to select more columns or even a SELECT * if you want to be able to display other values in this record.
To select the row with max 'popularity' column use this query;
$result = mysqli_query($con, "SELECT * FROM `comments` ORDER BY `popularity` DESC LIMIT 1");
In case you want all sorted by popularity remove the LIMIT 1...
You need
SELECT MAX(`popularity`) AS comment_id FROM `comments`
This will give the column the correct name for the associated array.
You are trying to read the result from a column named comment_id when the result from your query will be named MAX(popularity)
Run this query in mysql "SELECT MAX(popularity) FROM comments" first.The output of this gives you the index to use with $row[index] ie first row which in this case the index will be popularity else just change $row[content_id] to $row[popularity]
To get the total number of records, I usually use this query:
$total= mysql_num_rows(mysql_query("SELECT id FROM t_statistic WHERE pageid = $pid"));
but I got one the other query like below:
$data = mysql_fetch_object(mysql_query("SELECT COUNT(id) AS num_rows FROM t_statistic WHERE pageid = $pid"));
$total = $data->num_rows;
Between the two queries above. Which is more quickly and effectively (when the total number of records in the millions)?
I prefer the second query. It gives you already the record count, while the first query gives you the list of IDs (not the count), although it has been filtered but there are some cases when ID exist more than once in the table.
The Second query is quick and efficient:
SELECT COUNT(id) AS num_rows FROM t_statistic WHERE pageid = $pid
If you know about query optimisation. The query will only keeps only count in memory while calculating the answer. And directly gives number of rows.
Where as first query:
SELECT id FROM t_statistic WHERE pageid = $pid
Keeps all the selected rows in memory. then number of rows are calculated in further operation.
So second query is best in both ways.
Definitely the second one.
Some engines, like MySQL can do a count just by looking at an index rather than the table's data.
I've used something like the following on databases with millions of records.
SELECT count(*) as `number` FROM `table1`;
Way faster than: mysql_num_rows($res);
BTW: The * in Count(*) basically means it won't look at the data, it will just count the records, as opposed to Count(colname).
1) SELECT COUNT(*) FROM t_statistic WHERE pageid = $pid" --> count(*) counts all rows
2)SELECT COUNT(id) FROM t_statistic WHERE pageid = $pid" --> COUNT(column) counts non-NULLs only
3) SELECT COUNT(1) FROM t_statistic WHERE pageid = $pid" -->COUNT(1) is the same as COUNT(*) because 1 is a non-null expressions
Your use of COUNT(*) or COUNT(column) should be based on the desired output only.
So. Finally we have result is count(column) is more faster compare to count(*) .
I have a table as below,
ID Name Age
----------------------
100 A 10
203 B 20
Now how do i select only row1 using MySQL SELECT command and then I've to increase +1 to it to select row2. In short I'll be using for loop to do certain operations.
Thanks.
Sounds like you've got a mix up. You want to select all the rows you want to iterate through in your for loop with your query, and then iterate through them one by one using php's mysql functions like mysql_fetch_row
You should not try to use tables in a linear fashion like this. Set your criteria, sorting as appropriate, and then to select the next row use your existing criteria and limit it to one row.
SELECT * FROM `table` ORDER BY `ID` LIMIT 1
SELECT * FROM `table` ORDER BY `ID` WHERE ID > 100 LIMIT 1
You'd probably be better off retrieving all rows that you need, then using this. Note the LIMIT is entirely optional.
$query = mysql_query(' SELECT ID, Name, Age FROM table_name WHERE condition LIMIT max_number_you_want '))
while ($row = mysql_fetch_assoc($query)
{
// Do stuff
// $row['ID'], $row['Name'], $row['Age']
}
Lots of small queries to the database will execute much slower than one decent-sized one.
You should get the result into an array (php.net : mysql_fetch_*).
And after you'll can loop on the array "to do certain operations"
Yep, this is a pretty common thing to do in PHP. Like the others who have posted, here is my version (using objects instead of arrays):
$result = mysql_query("SELECT * FROM table_name");
while ($row = mysql_fetch_object($result)) {
// Results are now in the $row variable.
// ex: $row->ID, $row->Name, $row->Age
}
If I need to know the total number of rows in a table of database I do something like this:
$query = "SELECT * FROM tablename WHERE link='1';";
$result = mysql_query($query);
$count = mysql_num_rows($result);
Updated: I made a mistake, above is my actual way. I apologize to all
So you see the total number of data is recovered scanning through the entire database.
Is there a better way?
$query = "SELECT COUNT(*) FROM tablename WHERE link = '1'";
$result = mysql_query($query);
$count = mysql_result($result, 0);
This means you aren't transferring all your data between the database and PHP, which is obviously a huge waste of time and resources.
For what it's worth, your code wouldn't actually count the number of rows - it'd give you 2x the number of columns, as you're counting the number of items in an array representing a single row (and mysql_fetch_array gives you two entries in the array per column - one numerical and one for the column name)
SELECT COUNT(*) FROM tablename WHERE link='1';
You could just do :
SELECT count(*) FROM tablename;
for your query. The result will be a single column containing the number of rows.
If I need to know the total number of rows in a table of database
Maybe I'm missing something here but if you just want to get the total number of rows in a table you don't need a WHERE condition. Just do this:
SELECT COUNT(*) FROM tablename
With the WHERE condition you will only be counting the number of rows that meet this condition.
use below code
$qry=SHOW TABLES FROM 'database_name';
$res=mysql_query($qry);
$output=array();
$i=0;
while($row=mysql_fetch_array($res,MYSQL_NUM)){
++$i;
$sql=SELECT COUNT(*) FROM $row[0];
$output[$i]=mysql_query($sql);
}
$totalRows=array_sum($ouptput);
echo $totalRows;
http://php.net/manual/en/function.mysql-num-rows.php You need this i think.
If you are going to use the following SQL statement:
SELECT COUNT(*) FROM tablename WHERE link='1';
Make sure you have an index on the 'link' column