I have table with 10 columns and I want to check input value in where clause of the MySQL query.
I want to do something like this. But, when I use this query I am getting an error.
for example :
SELECT * FROM user_data
where poll_title='$poll_title'
and '$voter' IN (user_vote_1,user_vote_2,user_vote_3...user_vote_10)
order by idpoll ASC
user_vote_1 to 10 (value is null'ed in the database) and I want to retrieve only that rows from a column which have $voter value.
I think you need this comparison (Not Sure OfCourse) :-
SELECT * FROM user_data
where poll_title = "$poll_title"
and (user_vote_1 = "$voter"
OR user_vote_2 = "$voter"
OR user_vote_3 = "$voter"
OR user_vote_4 = "$voter"......OR user_vote_10 = "$voter")
order by idpoll ASC
If I've understood what you want to do - return only the column with the value - then would coalesce do the job? This assumes that the value in user_vote_n will either match the value you're looking for or be null, since coalesce returns the first non-null argument.
(untested)
select coalesce(user_vote_1, user_vote_2, user_vote_3, ) as UserVote from user_data
where coalesce(user_vote_1, user_vote_2, user_vote_3, ) = '$voter';
That aside, this looks like a structure that could do with normalising - a single 'user_vote' column and a single 'user_vote_number' column.
Related
I'm trying to update my first row in my database. I use the Limit 1 to only update the first row but nothing is happening. There are definitely matching rows but nothing changes in the database.
Here is the code:
foreach ($player_fromsite as $match_player_in_game) {
//$querytwo = 'INSERT INTO `'.$tablename.'` '.' (`'.$match_player_in_game.'`) '.'VALUES'.'("' . 'yes' . '")';
$querytwo = 'UPDATE '.$tablename.' SET `'.$match_player_in_game.'` = "'.'yes'.'" WHERE `'.$match_player_in_game.'` = "'.'NULL'.'" LIMIT 1';
$querythree = 'UPDATE '.$tablename.' SET `'.$match_player_in_game.'` = "'.'yes'.'" WHERE `'.$match_player_in_game.'` = "'.'NULL'.'" LIMIT 1';
for($a=0;$a<11;$a++){
if($match_player_in_game == $home_players[$a]){
// Insert a row of information into the table "example"
mysql_query($querytwo) or die(mysql_error());
}else{
mysql_query($querythree) or die(mysql_error());
}
}
}
Is the query correct?
In MySQL use IS NULL to compare with NULL.
For example: "UPDATE table SET field = 'yes' WHERE field IS NULL"
NULL isn't a string, so you shouldn't be using = 'NULL', unless you actually set it to that string value. Use IS NULL instead.
You need to define "first row". First row based on an autoincrementing id value? First based on a timestamp date? You need to specify this as MySQL has no concept of "first row".
For example, if you do something like this in MySQL:
SELECT * FROM table LIMIT 1
You are not guaranteed to get the same record back each time.
Most likely you will need to specify an ORDER BY condition on a key column, as without it, you have no guarantee of which row your LIMIT 1 will apply to. I really can't think of a case where one might use LIMIT without an ORDER BY clause, as the two really go hand in hand.
So your query should look like:
UPDATE table
SET field = 'yes'
WHERE field IS NULL
ORDER BY some_key_field ASC
LIMIT 1
Note that even this query would not update the same row every time. It would update the first record (as specified by ORDER BY) that has a NULL value for the specified field. So if you ran this query 10 times, it would change 10 different records (assuming there are that many records with NULL values).
This is my mysql query
$acountry = 1;
$this->db->where_in('varcountry', $acountry);
$val = $this->db->get('tblagencies')->result();
In database table the varcountry filed is stored like this 1,2,3,4 its type is varchar.Each row in table have multiple countries that is the reason to use varchar datatype.
Here i want to select table rows which have $acountry value in the filed varcountry.
How can i do that?The above code is it correct?
You have choosen a wrong data type for storing a comma separated value 1,2,3,4 into varchar,
you should chose a data-type of set, or normalize into a separate table, like :-
create table country (id, name ...);
create table agencies_country ( agency_id, country_id);
insert into agencies_country (agency_id, country_id)
values (x,1), (x,2), (x,3), (x,4);
// meaning 1,2,3,4 = 4 rows
// grabbing result using inner join
Using set is easier, but common practice is to normalize the data (which require some understanding).
I don't like the active record in codeigniter,
is easy to use (not doubt with this),
but it dis-allowed lost of flexibility
Personally I like the construct my own query,
provided you have the understanding of the table schema (which you have to anyway)
use this query..
$search_field = array('varcountry'=>$acountry)
$result = $this->db->get_where('tblagencies' , $search_field );
but in codeignator you can use your own queries like
$sql = "select * from tblagencies where varcountry like '%acountry%'";
$result = $this->db->query($sql);
I need to fetch a particular column value of a particular row using php in mysql.
For example if I want to fetch column2 value in row2, I tried using:
$qry = mysql_query("SELECT * from $table");
$data = mysql_fetch_row($qry);
$result = $data[1];
but this always returns only the first row value.
SELECT Column2
FROM $table
ORDER BY Something
LIMIT 1,1;
Or, if you know the key of the row
SELECT Column2
FROM $table
WHERE Key = Something
-- Optional: if you want 2nd after filtering
-- ORDER BY Something
-- LIMIT 1,1;
select COLUMNNAME from TABLENAME where ROWELEMENT="SOME_VALUE";
This should be your sql query..
You will need to access the value of that element using
$result['COLUMNNAME']
Complete code should look like this.
$query="select COLUMNNAME from TABLENAME where ROWELEMENT='SOME_VALUE'";
$result=mysql_query($query);
$result=mysql_fetch_array($result);
$columnvalue=$result['COLUMNNAME'];
Its bcoz mysql_query returns the result in an associative array form.
After the above code, You can access all elements like this.
$columnname[$index];
This will return the first value,
According to your question, You will need to first get the column values in a saperate array, and then access it using your index value..
I've a database that stores data read from different sensors. The table looks like this:
[SensorID][timestampMS][value]
[Sensor1][123420][10]
[Sensor1][123424][15]
[Sensor1][123428][6554]
[Sensor1][123429][20]
What I would like to do is the following: There are some reads that are corrupted (numbers that are 6554), and I would like to Update that with the next value that is not corrupted (in the example shown below that would be 20). So, if a number is 6554, I would like to update that with the next value (in timestamp), that is not corrupted.
I was thinking on doing this in PHP, but I wonder if it's possible to do it directly with a SQL script.
Appreciate :)
You can use a correlated sub-query...
UPDATE
myTable
SET
value = (SELECT value FROM myTable AS NextValue WHERE sensorID = myTable.SensorID AND timestampMS > myTable.timestampMS ORDER BY timestampMS ASC LIMIT 1)
WHERE
value = 6554
The sub-query gets all the following results, ordered by timestampMS and takes just the first one; That being the next value for that SensorID.
Note: If no "next" value exists, it will attempt to update with a value of NULL. To get around this, you can add this to the WHERE clause...
AND EXISTS (SELECT value FROM myTable AS NextValue WHERE sensorID = myTable.SensorID AND timestampMS > myTable.timestampMS ORDER BY timestampMS ASC LIMIT 1)
EDIT
Or, to be shorter, just use IFNULL(<sub_query>, value)...
Not sure if this is valid syntax, can't test it ATM. You may need to change this to be JOINs instead of the nested subqueries, but in concept you can do something like (for SQL Server):
UPDATE t1
SET Value = ( SELECT Value
from MyTable t2
WHERE t2.SensorID =t1.SensorID
AND t2.[timestamp] =
( SELECT MIN([TimeStamp])
FROM mytable t3
where t3.sensorid = t2.sensorID
AND t3.[timestamp] > t2.[timestamp]
)
)
FROM Mytable t1
WHERE t1.value = 6554
I did a workaround based on Dems solution, and it works in Mysql:
I've created a "copy" of the sensors table like this:
drop table if exists sensors_new;
create table if not exists sensors_new like sensors;
insert into sensors_new select * from sensors;
Then I do what Dems recommended me doing, but using this new aux table in the select (to avoid the error that Mysql launches when Updating a table while doing a select in the same table).
UPDATE
sensors
SET
raw_data = (SELECT raw_data FROM sensors_new AS NextValue WHERE sensor_id = sensors.sensor_id AND timestampMS > sensors.timestampMS ORDER BY timestampMS ASC LIMIT 1)
WHERE
value = 6554
Then, just drop this auxiliar table.
I hope this helps Mysql users.
I have a database field know as SCORES which has Scores
the value may be like the following
123
14
56*
342
423*
I am storing that in a Varchar Field in the database.
Suppose If I convert that to a integer a datatype, then I can write
max(SCORES) and get the Maximum score or Highest Scores.
But Integer doesnot allow special character like *.
(Here * represent some clause for that scores)
To accomadate that I have made that to the varchar.
What will be best way to get the Highest score very easily with minimum programming method.
So that If I execute a query I should be get the answer as
423*
Please suggest me
The best way to handle this situation is to change you table structure to make
SCORES of int data type.
Add a new field in the table called
clause
If most of your SCORES are without a
clause, you must normalize the table
to move the clause field to a
different table.
You should change table schema ...
SELECT scores
FROM tablename
ORDER BY replace(scores, '*', '') DESC
LIMIT 1;
I think your query should be generic for getting maximum score, today you have only '*' is attached with score but in future may be you use some others character or may be you use some combination of character so you should take care of that scenario.
so i thing it will be better if you create a user define function which takes varchar as a input and return number from input string like if you pass '1234*' then function will return 1234 and if you pass 1234** it will return 1234.
CREATE FUNCTION dbo.ParseNumeric
(
#string VARCHAR(8000)
)
RETURNS VARCHAR(8000)
AS
BEGIN
DECLARE #IncorrectCharLoc SMALLINT
SET #IncorrectCharLoc = PATINDEX('%[^0-9A-Za-z]%', #string)
WHILE #IncorrectCharLoc > 0
BEGIN
SET #string = STUFF(#string, #IncorrectCharLoc, 1, '')
SET #IncorrectCharLoc = PATINDEX('%[^0-9]%', #string)
END
SET #string = #string
RETURN #string
END
GO
then use:
select max(cast(dbo.ParseNumeric(score) as int)) from tableName
SELECT MAX(CAST(scores AS SIGNED))
FROM tablename
But this query will be quite slow, since it cannot be optimized using indexes.
You could move the asterisk to a new field (depends if you need it or not). After that you can change the datatype.
UPDATE
tableName
SET
score = REPLACE(score, '*', ''),
specialCharField = IF(CONTAINS(score, '*'), '*', '');
Try this SQL:
SELECT MAX(CONVERT(REPLACE(FIELD,'*',''),signed)) FROM TABLE
It:
Replace the * from your varchar
Covnert the result into integer (signed)
Select the MAX value
EDIT 1:
I have been tring the SQL with some data, i have a table with one field (varchar, no key), I've inserted 62962 values (one each 1000 have a '*', the results as follow :)
SELECT MAX(CONVERT(REPLACE(FIELD,'*',''),signed)) FROM TABLE
Took 0.0666sec.
SELECT scores FROM tablename ORDER BY replace(scores, '*', '') DESC LIMIT 1;
Took 0.089sec to execute and got the wrong value:
HTH :)