Suppose I have the next table structure, table A:
| id |
|----|
| 3 |
| 4 |
| 7 |
Table B:
| id | title | last_id |
|----|-------|---------|
| 1 | a | 1 |
| 2 | b | 2 |
| 3 | c | 3 |
I want to change Table's B last_id to the next matching id from Table A.
Example: (Referring to Table's B first row)
Current last_id is 1, So I need to forward it's value to the next, bigger id from Table A.
So it will go:
1 -> 3 -> 4 -> 7
It can be done also with PHP, but maybe there is a way to keep it in the SQL Server.
Thanks in advance.
NOTE: The server runs MySQL.
Previous answer is correct, but the +1 I believe is no needed as you just need value 7
UPDATE table_b
SET last_id = (SELECT MAX(id) FROM table_a)
Edited:
Now it picks the minimum value from table_a bigger that the last_id on table_b
UPDATE table_b
SET last_id = (SELECT MIN(id) FROM table_a WHERE id>last_id)
The following snippets are pseudo code.
Grab the next table_a id:
SELECT id FROM table_a WHERE id > $currentLastId ORDER BY id ASC LIMIT 1
If not null, update your table_b last_id column.
Example: (Referring to table_b first row)
The SQL query would be:
SELECT id FROM table_a WHERE id > 1 ORDER BY id ASC LIMIT 1
It would return 3.
Related
I have a database with this table
+------+---------------------+-------------+
| id | key | value |
+------+---------------------+-------------+
| 152 | incidencia_0_fecha | 20150306 |
| 158 | incidencia_1_fecha | 20150307 |
| 234 | incidencia_2_fecha | 20150309 |
| . | ...... | ........ |
| n | incidencia_N_fecha | date_value |
+------+---------------------+-------------+
And I want to know what is the last key (N its dinamic and i don't know his last value). In this table the last must be incidencia_2_fecha.
How can i do it?
Thanks
You can easily get the number in the string using two REPLACES.
SELECT MAX(
REPLACE(REPLACE(`key`, 'incidencia_', ''), '_fecha', '')
)
FROM mytable
If the values in the id column are strictly increasing, you can do this:
SELECT key FROM your_table WHERE id = (SELECT MAX(id) FROM your_table);
EDIT 1:
If the table is quite large, you should make sure that there's an index on the id column. Otherwise the query could take a long time to run.
EDIT 2:
Another option, if the value column contains the date at the time the record was inserted (and is indexed), would be to do the above query, but replace id with value, i.e.
SELECT key FROM your_table WHERE value = (SELECT MAX(value) FROM your_table);
First fetch record in desc
SELECT key from tbl_name ORDER BY id DESC LIMIT 0,1
plan_id | elementclass | table_no | ress_id | UserID | Status
1 | elementclass1 | 1 | 0 | 0006100022 | N
1 | elementclass1 | 1 | 2 | 0006100022 | N
1 | elementclass2 | 2 | 0 | 0006100021 | N
1 | elementclass4 | 3 | 0 | 0006100023 | N
in above row I am expecting as this
if row is having same elementclass,table_no but different ress_id in that condition only take that row which is non zero.If with above condition tow rows having 0 it can take any row .if both rows have non zero then also it can take any one.
Now
for rest of others it can take values with 0.We can use group by to plan_id as there may be multiple plans.
Desired result
plan_id | elementclass | table_no | ress_id | UserID | Status
1 | elementclass1 | 1 | 2 | 0006100022 | N
1 | elementclass2 | 2 | 0 | 0006100021 | N
1 | elementclass4 | 3 | 0 | 0006100023 | N
Please help.
thanks
SELECT * FROM TableName a
WHERE a.ress_id = (SELECT MAX(b.ress_id) FROM TableName b WHERE b.table_no = a.table_no)
GROUP BY a.plan_id,a.table_no
This gives you:
1 result per plai_id and table_no
each result has biggest ress_id in it
First get the maximum ress id per element class. Then select the related records. There may be duplicates. Hence group by element class and ress id.
The following statement does not precisely do what you asked for, but maybe it suffices. In case of a tie you won't get one of the records, but one of the records' plan ids, one of the records' table nos, one of the records' user ids and one of the records' statusses. So the user id may be taken from one record and the status from another when elementclass and ress_id are equal.
select plan_id, mytable.elementclass, table_no, mytable.ress_id, userid, status
from mytable
join
(
select elementclass, max(ress_id) as max_ress_id
from mytable
group by elementclass
) agg on agg.elementclass = mytable.elementclass and agg.max_ress_id = mytable.res_id
group by mytable.elementclass, mytable.ress_id;
(It is possible to write a statement to access complete records in case of ties, but this is much more complicated - at least in MySQL.)
Try this:
SELECT T1.*
FROM TableName T1 JOIN
(SELECT elementclass,table_no,MAX(ress_id) as ress_id
FROM TableName
GROUP BY elementclass,table_no
)T2 ON T1.elementclass=T2.elementclass AND T1.table_no=T2.table_no AND T1.ress_id=T2.ress_id
Explanation:
Here, we are creating a temporary table T2 with maximum of ress_id for each elementclass and table_no. Then we join this table with the original table with these 3 fields and select all records from the original table T1.
Result:
PLAN_ID ELEMENTCLASS TABLE_NO RESS_ID USERID STATUS
-------------------------------------------------------------------
1 elementclass1 1 2 0006100022 N
1 elementclass2 2 0 0006100021 N
1 elementclass4 3 0 0006100023 N
See result in SQL Fiddle.
In a table i have some of column have duplicate values i want to retrieve unique values from my table i used SELECT DISTINCT column_name FROM table_name query and i got unique columns but my problem is i also want id of anyone of the duplicate value how can i retrieve that from using a single query ?
Eg
+----+------+------+
| id | name | po |
+----+------+------+
| 1 | some | 2 |
| 2 | xyzs | 3 |
| 3 | frth | 2 |
| 4 | lopd | 3 |
| 5 | gtry | 2 |
+----+------+------+
i want to find unique po and any one of its id
Output
some thing like this
po - 2 id - ( any of 1,3,5)
po - 3 id - ( any of 2 or 4)
Just group them and get the max id or the min.
SELECT max(id), po FROM table_name group by po
try this:
SELECT MIN(id) id, po
FROM table_name
GROUPB BY po, id
Don't quote me on this, but you might be able to do something like:
SELECT GROUP_CONCAT(id) FROM table_name GROUP BY po
If you don't care which id you will get, then:
SELECT po,id FROM table GROUP BY po
If you wish to get first/last of the ids with that same po, you can add MIN(id)/MAX(id) as well:
SELECT po,MIN(id) as id FROM table GROUP BY po
You can also have all the ids for that po:
SELECT po,GROUP_CONCAT(id) as ids FROM table GROUP BY po
My table will hold scores and initials.
But the table wont be ordered.
I can get the total row count easy enough and I know I can get all of them and Order By and then loop through them and get the rank THAT way...
But is there a better way? Could this maybe be done with the SQL statement?
I'm not TOO concerned about performance so if the SQL statement is some crazy thing, then Ill just loop.
Sorry - Table has id as primary key, a string to verify unique app install, a column for initials and a column for score.
When someone clicks GET RANK... I want to be able to tell them that their score is 100 out of 1000 players.
SELECT s1.initials, (
SELECT COUNT(*)
FROM scores AS s2
WHERE s2.score > s1.score
)+1 AS rank
FROM scores AS s1
Do you have a primary key for the table or are you fetching data by the initials or are you just fetching all the data and looping through it to get the single record? How many results are you trying to fetch?
If you only want to fetch one record, as the title suggests, you would query the database using a WHERE conditional:
SELECT score FROM table WHERE user_id = '1';
See this answer: https://stackoverflow.com/a/8684441/125816
In short, you can do something like this:
SELECT id, (#next_rank := IF(#score <> score, 1, 0)) nr,
(#score := score) score, (#r := IF(#next_rank = 1, #r + 1, #r)) rank
FROM rank, (SELECT #r := 0) dummy1
ORDER BY score DESC;
And it will produce a result like this:
+------+----+-------+------+
| id | nr | score | rank |
+------+----+-------+------+
| 2 | 1 | 23 | 1 |
| 4 | 1 | 17 | 2 |
| 1 | 0 | 17 | 2 |
| 5 | 1 | 10 | 3 |
| 3 | 1 | 2 | 4 |
+------+----+-------+------+
Note that users with equal scores have equal ranks. :-)
I have a table with details on personnel. I would like to create a Next/Previous link based on the individual's last name. Since personnel were not added in alphabetical order, selecting the next or previous row based on its ID does not work.
It is a hefty table - the pertinent fields are id, name_l, and name_f. I would like to order by name_l, the individuals' last name.
How would I go about accomplishing this task?
Thanks!
Edit
This will be used on a Personnel Details page, the result will generate links to the next/prev entry in the database (ordered by last name) based on the current row. For example, if I am viewing Joe Hammer, the Next link would link to Frank Ingram.
Final code
Thanks to Daniel, here is what I finally got to work:
First, I set an increment at 0: $i = 0. Then, while looping through records with a while loop, I increased this by 1 = $i++. I then made a link to the details page for that particular entry:
Details
On the Details page, I used the following SQL to select the next record:
$row = $_GET['row'];
$getNext = mysql_query("SELECT * FROM members ORDER BY name_l, id LIMIT ".$row.", 1");
$next = mysql_fetch_assoc($getNext);
$nextLink = $row + 1;
Finally, the link:
<?php echo $next['name_l'] . ", " . $next['name_f'];?>
First of all, make sure that your name_l column is indexed. Then you can simply use the ORDER BY and the LIMIT clauses as follows:
SELECT * FROM personnel ORDER BY name_l, id LIMIT 0, 1;
Simply increment the 0 value in the LIMIT clause to select the next record within the ordered set. Therefore use LIMIT 1, 1 to get the second record, LIMIT 2, 1 for the third, etc.
To create an index on name_l you can use the CREATE INDEX command:
CREATE INDEX ix_index_name ON personnel (name_l);
Test case:
CREATE TABLE personnel (
id int not null primary key,
name_l varchar(10),
name_f varchar(10)
);
CREATE INDEX ix_last_name_index ON personnel (name_l);
INSERT INTO personnel VALUES (1, 'Pacino', 'Al');
INSERT INTO personnel VALUES (2, 'Nicholson', 'Jack');
INSERT INTO personnel VALUES (3, 'De Niro', 'Robert');
INSERT INTO personnel VALUES (4, 'Newman', 'Paul');
INSERT INTO personnel VALUES (5, 'Duvall', 'Robert');
Results:
SELECT * FROM personnel ORDER BY name_l, id LIMIT 0, 1;
+----+---------+--------+
| id | name_l | name_f |
+----+---------+--------+
| 3 | De Niro | Robert |
+----+---------+--------+
1 row in set (0.00 sec)
SELECT * FROM personnel ORDER BY name_l, id LIMIT 1, 1;
+----+--------+--------+
| id | name_l | name_f |
+----+--------+--------+
| 5 | Duvall | Robert |
+----+--------+--------+
1 row in set (0.00 sec)
SELECT * FROM personnel ORDER BY name_l, id LIMIT 2, 1;
+----+--------+--------+
| id | name_l | name_f |
+----+--------+--------+
| 4 | Newman | Paul |
+----+--------+--------+
1 row in set (0.00 sec)
1st UPDATE: (Further to the comments below)
The above example is suitable mainly if you start by displaying the first record, and then you move sequentially to next, and maybe next again, and perhaps one back, etc. You could also easily move x steps forward and x steps backwards, but this does not appear to be required.
If you start from a random record however, it will be more difficult to adapt the query above to get the next and previous records.
If this is the case, then you can simply keep an index counter of where you currently stand. You start with $index = 0, and display the first record by using ... LIMIT $index, 1. Then you display the next by incrementing $index by 1, and you display the previous by decrementing $index by 1.
If on the other hand, you will be rendering the personnel list, and then the user will click on one record (at random), you could also make this work with some help from the applications-side (php). Let's say you render the following ordered list to the user:
+----+-----------+--------+
| id | name_l | name_f |
+----+-----------+--------+ // [Hidden info]
| 3 | De Niro | Robert | // Row 0
| 5 | Duvall | Robert | // Row 1
| 4 | Newman | Paul | // Row 2
| 2 | Nicholson | Jack | // Row 3
| 1 | Pacino | Al | // Row 4
+----+-----------+--------+
Now if the user clicks on Newman Paul, you would have to pass the row=2 parameter to the page that will display the details of this employee. The page that renders the details of the employee now knows that Newman Paul is the 3rd row (row=2). Therefore to get the previous and the next records you would simply change the x in LIMIT x, 1 by row - 1 for the previous record and row + 1 for the next:
-- Previous
SELECT * FROM personnel ORDER BY name_l, id LIMIT 1, 1;
+----+--------+--------+
| id | name_l | name_f |
+----+--------+--------+
| 5 | Duvall | Robert |
+----+--------+--------+
1 row in set (0.00 sec)
-- Next
SELECT * FROM personnel ORDER BY name_l, id LIMIT 3, 1;
+----+-----------+--------+
| id | name_l | name_f |
+----+-----------+--------+
| 2 | Nicholson | Jack |
+----+-----------+--------+
1 row in set (0.00 sec)
2nd UPDATE:
You can use the following MySQL-specific query to get the record number within the ordered list of any random employee, which then can be used to get the previous and next records. Note however that this is not very efficient, and may degrade performance if you have thousands of records.
Let's say you are in employee Nicholson Jack.
You could do the following query:
SELECT p.id, p.name_l, p.name_f, o.record_number
FROM personnel p
JOIN (
SELECT id,
#row := #row + 1 AS record_number
FROM personnel
JOIN (SELECT #row := -1) r
ORDER BY name_l, id
) o ON (o.id = p.id)
WHERE p.name_l = 'Nicholson' AND p.name_f = 'Jack';
Which returns this:
+----+-----------+--------+---------------+
| id | name_l | name_f | record_number |
+----+-----------+--------+---------------+
| 2 | Nicholson | Jack | 3 |
+----+-----------+--------+---------------+
1 row in set (0.00 sec)
Note that in the WHERE clause you could have used p.id = 2 if the id is known, instead of p.name_l = 'Nicholson' AND p.name_f = 'Jack'.
Now we can use the record_number field, which is 3 in this case, to get the previous and the next records, simply by using the original query from the top of this answer, and replacing LIMIT 2, 1 for the previous and LIMIT 4, 1 for the next. There you go:
The previous of Nicholson Jack:
SELECT * FROM personnel ORDER BY name_l, id LIMIT 2, 1;
+----+--------+--------+
| id | name_l | name_f |
+----+--------+--------+
| 4 | Newman | Paul |
+----+--------+--------+
1 row in set (0.00 sec)
The next from Nicholson Jack:
SELECT * FROM personnel ORDER BY name_l, id LIMIT 4, 1;
+----+--------+--------+
| id | name_l | name_f |
+----+--------+--------+
| 1 | Pacino | Al |
+----+--------+--------+
1 row in set (0.00 sec)
Try a better SQL SELECT statement:
SELECT * FROM tblPersonnel ORDER BY name_l ASC
Try this link for more info:
http://w3schools.com/sql/sql_orderby.asp