I have an MsSQL server and what I am doing is selecting rows from the table. Currently I have two rows so I was wondering how would I check if there are no other rows after second one without making another query?
For example
table users
id name pass
1 joe 123
2 bob abc
How would I check if there is no row after 2 with just a query? I am willing to combining it with my current query, which just selects the data.
You can return the number of rows in your query as another column:
SELECT id, name, pass, count(*) over () as rows
FROM users
Keep in mind that this is telling you the number of rows returned by the query, not the number of rows in the table. However, if you specify a "TOP n" in your select, the rows column will give you the number of rows that would have been returned if you didn't have "Top n"
If you're trying to paginate the trick is to query one more record than you actually need for the current page. By counting the result (mysql_num_rows) and comparing that to your page size, you can then decide if there is a 'next page'.
If you were using mysql you could also use SQL_CALC_FOUND_ROWS() in your query, which calculates the number of rows that would be returned without the LIMIT clause. Maybe there is an equivalent for that in MsSQL?
I assume that you are inserting manually the first 2 rows of your table.
According to that, my idea is to just do a select where the id is more than 2 like this:
SELECT * FROM users WHERE id > 2;
I also assume that you are using PHP so mysql_num_rows will return you 0 if no data is found, otherwise it will return you the number of rows from your query and now you know that you need to do a while or some loop to retrieve the data after id number 2.
Related
Hi so I'm fetching in two almost identical rows from my db
So what I what do do is to check if there is two equal rows with the same name for extra_field if there is, it should only show the row where it has the bku_id.
Here is the object in php, where I want the code to execute that:
If you are using SQL you can use this query -
SELECT * FROM <your_table> GROUP BY extra_field HAVING bku_id IS NOT NULL
I have been working on my "administrative" webpage for a while now, almost finished. Just need a little help with one last thing;
I want to get a value (ID) from a table posted as Yes if the ID is found, but no if it isn't.
Have managed to get it printet, but it prints all the records in the table on every person that displays on the website (http://gyazo.com/13f271bbb8c4e83ff9ecd9908545c854 where it says "Betalt" it should just be ONE correct for each one).
The code for that part is here:
if ($row[9] == $row[1]) {
$betalt = "Ja";
}
$row[9] is the value from table SI_PAYMENTS. And $row[1] is the value from table BUSS1.
These two values should be the same if the record exists in SI_PAYMENTS, and if it exists, I want the webpage to display "Yes". But if it don't find it, I want the webpage to display "No".
EDIT
Here's my SQL Query:
SELECT buss1.navn, buss1.plassnummer, buss1.telefon, buss1.epost, buss1.fodselsdato, buss1.pastigningssted, buss1.bilettype, buss1.ankommet, buss1.merknader, si_payment.ac_inv_id FROM buss1, si_payment ORDER BY buss1.plassnummer ASC
I think you need to JOIN the two tables. At the moment, you will get every row from table buss1 next to every row from si_payment. So if there are 6 rows in buss1 and 4 in si_payment, you'll end up with 24 rows. I suspect there is a column in the two tables that links them, so you need a JOIN: something like this
SELECT buss1.navn, buss1.plassnummer, buss1.telefon, buss1.epost, buss1.fodselsdato, buss1.pastigningssted, buss1.bilettype, buss1.ankommet, buss1.merknader, si_payment.ac_inv_id
FROM buss1 INNER JOIN si_payment WHERE buss1.some_column = si_payment.another_column
ORDER BY buss1.plassnummer ASC
I can't tell what some_column and another_column should be, I'm afraid. But if you change those, that will give you only the matching rows from the two tables. If that's not quite right, you may need a LEFT JOIN, which will give you all rows from the first table and the matching rows from the same table.
If I've misunderstood, I apologise.
The code:
$review = mysql_query("SELECT conceptID, MIN(nextReview) FROM userconcepts WHERE userID='$userID'");
$nrows = mysql_num_rows($review);
echo "$nrows<br />\n";
The query works when the table has such entries and returns the correct column values. However, when the table is empty, as I can confirm right now in HeidiSQL, mysql_num_rows still returns 1, but the column values are empty. (The problem still remains if the table has other values for different userIDs).
I expect this query to return the empty set sometimes during normal operations, and I want to take action based on the existence of a result, but I also want to use the result if it exists. Any idea why this code is not working as I expect it to work (I expect it to return 0 if the table is empty)?
First of all, the query has a very simple problem: you're showing the conceptID field, but not grouping by it. If you want to show a field on a SELECT that uses aggregate functions, you should show it; not doing so is an error, and will make many engines not execute your query.
That aside, whenever you have an aggregate function, and you don't group by anything (i.e., don't add a GROUP BY clause), the result is one row. Regardless of the amount of rows in the table.
The reason why is because when a SQL engine executes a query with only aggregation functions, then it returns one row. So:
select count(*)
from table
where 1 = 2
is going to return 1 row with the value 0. This is the way that all SQL engines work.
Your query is a little different:
select conceptID, MIN(nextReview)
FROM userconcepts
WHERE userID='$userID'"
In most SQL dialects, you would get an error of the from "conceptID not in group by clause" or something like that. That is, the query would have a syntax error.
MySQL supports this. It will return the minimum value of nextReview (from the rows that meet the where condition) along with an arbitrary value of conceptID (from those same rows). In this case, there are no rows, so the values will be set to NULL.
Perhaps, you want one row per conceptId. That query would be:
select conceptID, MIN(nextReview)
FROM userconcepts
WHERE userID='$userID'
group by conceptId
I have a query and a loop written that lists all the rows from a mysql table ("records") formatted in a HTML table.
One of the fields is "subject_id" which is an integer. I also have a table named "subjects" which corresponds to the same "subject_id" in the records table. Only two fields are in the "subjects" table, is an auto-index ID integer and a varchar(1024) for the subject title.
The value that returns from the "records" table is an integer. I want to perform a lookup on the integer from the "records" table for each row to output the text equivalent from the "subject_id" field.
My first notion, the kindergarten way, would be to throw in another query within the loop, effectively increasing my number of queries from 300 to 600 to load the page (no pagination is needed).
What would be a better way of this "sub query" aside from adding 300 more queries?
Edit:
I'm pulling the data from the table using a while loop and echoing my variable $r_subject (from: $r_subject = mysql_result($result,$a,"subject");). The value returned from the initial records table is INT. I want to take the $r_subject and then check it against the SUBJECTS table to get the string name associated with that INT id.
It's hard to know exactly what you need without seeing code, but from what I gather, you have 2 tables, one has the ID, the other has the text, so you would want to use a join.
The second thing is, you'll want to look at whether or not you really need 300 queries in the first place. That's a lot of queries to run and you should only need to run that many queries when you're running a bulk insert/update or something of that nature; other than that, you most likely could reduce that number substantially.
select
A.*,
B.title
from
records A,
subjects B
where
B.subject_id = A.subject_id
That's a single query that will produce all of the data you need for your page.
select
subjects.SubjectTitle,
records.whateverFieldYouWant,
records.AnyOtherField
from
records
join subjects
on records.subject_id = subjects.subject_id
where
records.subject_id = TheOneSubjectYouWant
but can't confirm without actual structure of tables and some sample data displayed showing proper context of what you are expecting out
Is it possible in php to return a specific row of data from a mysql query?
None of the fetch statements that I've found return a 2 dimensional array to access specific rows.
I want to be able to return only 1 specific row, kinda like mysql_result... except for entire row instead of 1 cell in a row.
I don't want to loop through all the results either, I already know how to do that I just thought that there might be a better way that I'm not aware of. Thanks
For example, mysql_data_seek() and mysqli_stmt_data_seek() allow you to skip forward in a query result to a certain row.
If you are interested in one certain row only, why not adapt the query to return only the row you need (e.g. via a more specific WHERE clause, or LIMIT)? This would be more resource-effective.
You should add LIMIT to your mysql statement. And it will return only data you need. Like following:
-- returns 1 row after 2 row
SELECT * FROM table LIMIT 2, 1