I have mysql with a user table with answers from a poll saved as a bitwise. How do I find the user with most or least common answers with the reference bitwise?
+------+---------+--+
| User | Answers | |
+------+---------+--+
| A | 1 | |
| B | 5 | |
| C | 10 | |
+------+---------+--+
Assuming by 'reference bitwise' you mean that you have another value that is a bitmask that you are trying to match against the Answers column, something like this should do it for you. In this case, I'm using '4' as the reference bitmask and myTable as the name of your table..
SELECT User, BIT_COUNT(Answers & 4) AS MatchedBits FROM myTable ORDER BY MatchedBits DESC
This returns:
+------+-------------+
| User | MatchedBits |
+------+-------------+
| B | 1 |
| A | 0 |
| C | 0 |
+------+-------------+
You can also add a LIMIT 1 clause to get just the top result, but of course that won't tell you if there is more than one top result with the same number of bits matched.
Related
I want to select value from table sorted by a certain order.
I have a table called test that looks like this:
| date | code | value |
+----------+-----------+----------+
| 20050104 | 000005.SZ | -6359.19 |
| 20050104 | 600601.SH | -7876.34 |
| 20050104 | 600602.SH | -25693.3 |
| 20050104 | 600651.SH | NULL |
| 20050104 | 600652.SH | -15309.9 |
...
| 20050105 | 000005.SZ | -4276.28 |
| 20050105 | 600601.SH | -3214.56 |
...
| 20170405 | 000005.SZ | 23978.13 |
| 20170405 | 600601.SH | 32212.54 |
Right now I want to select only one date, say date = 20050104, and then sort the data by a certain order (the order that each stock was listed in the stock market).
I have another table called stock_code which stores the correct order:
+---------+-----------+
| code_id | code |
+---------+-----------+
| 1 | 000002.SZ |
| 2 | 000004.SZ |
| 3 | 600656.SH |
| 4 | 600651.SH |
| 5 | 600652.SH |
| 6 | 600653.SH |
| 7 | 600654.SH |
| 8 | 600602.SH |
| 9 | 600601.SH |
| 10 | 000005.SZ |
...
I want to sorted the selected data by stock_code(code_id), but I don't want to use join because it takes too much time. Any thoughts?
I tried to use field but it gives me an error, please tell me how to correct it or give me an even better idea.
select * from test
where date = 20050104 and code in (select code from stock_code order by code)
order by field(code, (select code from stock_code order by code));
Error Code: 1242. Subquery returns more than 1 row
You told us that you don't want to join because it takes too much time, but the following join query is probably the best option here:
SELECT t.*
FROM test t
INNER JOIN stock_code sc
ON t.code = sc.code
WHERE t.date = '20050104'
ORDER BY sc.code_id
If this really runs slowly, then you should check to make sure you have indices setup on the appropriate columns. In this case, indices on the code columns from both tables as well as an index on test.date should be very helpful.
ALTER TABLE test ADD INDEX code_idx (code)
ALTER TABLE test ADD INDEX date_idx (date)
ALTER TABLE code ADD INDEX code_idx (code)
As I said in the title, or maybe my question is a little bit confusing. Here it is....
So, I want to combine 2 tables using INNER JOIN (ofcourse) with some difference.
This is my tables
Table 1, PK = steam_id
SELECT * FROM nmrihstats ORDER BY points DESC LIMIT 4;
+---------------------+----------------+--------+-------+--------+
| steam_id | name | points | kills | deaths |
+---------------------+----------------+--------+-------+--------+
| STEAM_0:1:88467338 | Alan14 | 50974 | 5438 | 12 |
| STEAM_0:0:95189481 | ? BlacKEaTeR ? | 35085 | 24047 | 316 |
| STEAM_0:1:79891668 | Lowell | 34410 | 44076 | 993 |
| STEAM_0:1:170948255 | Rain | 29780 | 30167 | 278 |
+---------------------+----------------+--------+-------+--------+
4 rows in set (0.01 sec)
Table 2, PK = authid
SELECT * FROM store_players ORDER BY credits DESC LIMIT 4;
+-----+-------------+---------------+---------+--------------+-------------------+
| id | authid | name | credits | date_of_join | date_of_last_join |
+-----+-------------+---------------+---------+--------------+-------------------+
| 309 | 1:88467338 | Alan14 | 15543 | 1475580801 | 1482260232 |
| 368 | 1:79891668 | Lowell | 10855 | 1475603908 | 1482253619 |
| 256 | 1:128211488 | Fuck[U]seLF | 10422 | 1475570061 | 1482316480 |
| 428 | 1:74910707 | Mightybastard | 7137 | 1475672897 | 1482209608 |
+-----+-------------+---------------+---------+--------------+-------------------+
4 rows in set (0.00 sec)
Now, how can I use INNER JOIN without doing like removing "STEAM_0:" or adding it. Also with explanation, please
You can join witn like operator, e.g.:
SELECT n.*, sp.*
FROM nmrihstats n JOIN store_players sp ON n.steam_id LIKE CONCAT('%', sp.authid);
Here's the SQL Fiddle.
Another approach would be to use String functions of MySQL to extract out relevant part from steam_id but I believe that's not what you want:
SELECT SUBSTR(steam_id, LOCATE('STEAM_0:', steam_id) + CHAR_LENGTH('STEAM_0:'))
FROM nmrihstats;
it is not possible, you need to remove "STEAM_0:", matching with WHERE, using substring for remove STEAM_0: from column equals to column in other table, or a new field into the T1 without "STEAM_0:", that 2 columns match for INNER JOIN
I'm feeling a little rusty with creating queries in MySQL. I thought I could solve this, but I'm having no luck and searching around doesn't result in anything similar...
Basically, I have two tables. I want to select everything from one table and the matching row from the second table. However, I only want to have the first result from the second table. I hope that makes sense.
The rows in the daily_entries table are unique. There will be one row for each day, but maybe not everyday. The second table notes contains many rows, each of which are associated with ONE row from daily_entries.
Below are examples of my tables;
Table One
mysql> desc daily_entries;
+----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+----------------+
| eid | int(11) | NO | PRI | NULL | auto_increment |
| date | date | NO | | NULL | |
| location | varchar(100) | NO | | NULL | |
+----------+--------------+------+-----+---------+----------------+
Table Two
mysql> desc notes;
+---------+---------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+---------+------+-----+---------+----------------+
| task_id | int(11) | NO | PRI | NULL | auto_increment |
| eid | int(11) | NO | MUL | NULL | |
| notes | text | YES | | NULL | |
+---------+---------+------+-----+---------+----------------+
What I need to do, is select all entries from notes, with only one result from daily_entries.
Below is an example of how I want it to look:
+----------------------------------------------+---------+------------+----------+-----+
| notes | task_id | date | location | eid |
+----------------------------------------------+---------+------------+----------+-----+
| Another note | 3 | 2014-01-02 | Home | 2 |
| Enter a note. | 1 | 2014-01-01 | Away | 1 |
| This is a test note. To see what happens. | 2 | | Away | 1 |
| Testing another note | 4 | | Away | 1 |
+----------------------------------------------+---------+------------+----------+-----+
4 rows in set (0.00 sec)
Below is the query that I currently have:
SELECT notes.notes, notes.task_id, daily_entries.date, daily_entries.location, daily_entries.eid
FROM daily_entries
LEFT JOIN notes ON daily_entries.eid=notes.eid
ORDER BY daily_entries.date DESC
Below is an example of how it looks with my query:
+----------------------------------------------+---------+------------+----------+-----+
| notes | task_id | date | location | eid |
+----------------------------------------------+---------+------------+----------+-----+
| Another note | 3 | 2014-01-02 | Home | 2 |
| Enter a note. | 1 | 2014-01-01 | Away | 1 |
| This is a test note. To see what happens. | 2 | 2014-01-01 | Away | 1 |
| Testing another note | 4 | 2014-01-01 | Away | 1 |
+----------------------------------------------+---------+------------+----------+-----+
4 rows in set (0.00 sec)
At first I thought I could simply GROUP BY daily_entries.date, however that returned only the first row of each matching set. Can this even be done? I would greatly appreciate any help someone can offer. Using Limit at the end of my query obviously limited it to the value that I specified, but applied it to everything which was to be expected.
Basically, there's nothing wrong with your query. I believe it is exactly what you need because it is returning the data you want. You can not look at as if it is duplicating your daily_entries you should be looking at it as if it is return all notes with its associated daily_entry.
Of course, you can achieve what you described in your question (there's an answer already that solve this issue) but think twice before you do it because such nested queries will only add a lot of noticeable performance overhead to your database server.
I'd recommend to keep your query as simple as possible with one single LEFT JOIN (which is all you need) and then let consuming applications manipulate the data and present it the way they need to.
Use mysql's non-standard group by functionality:
SELECT n.notes, n.task_id, de.date, de.location, de.eid
FROM notes n
LEFT JOIN (select * from
(select * from daily_entries ORDER BY date DESC) x
group by eid) de ON de.eid = n.eid
You need to do these queries with explicit filtering for the last row. This example uses a join to do this:
SELECT n.notes, n.task_id, de.date, de.location, de.eid
FROM daily_entries de LEFT JOIN
notes n
ON de.eid = n.eid LEFT JOIN
(select n.eid, min(task_id) as min_task_id
from notes n
group by n.eid
) nmin
on n.task_id = nmin.min_task_id
ORDER BY de.date DESC;
Some background: an 'image' is part of one 'photoshoot', and may be a part of zero or many 'galleries'. My tables:
'shoots' table:
+----+--------------+
| id | name |
+----+--------------+
| 1 | Test shoot |
| 2 | Another test |
| 3 | Final test |
+----+--------------+
'images' table:
+----+-------------------+------------------+
| id | original_filename | storage_location |
+----+-------------------+------------------+
| 1 | test.jpg | store/test.jpg |
| 2 | test.jpg | store/test.jpg |
| 3 | test.jpg | store/test.jpg |
+----+-------------------+------------------+
'shoot_images' table:
+----------+----------+
| shoot_id | image_id |
+----------+----------+
| 1 | 1 |
| 1 | 2 |
| 3 | 3 |
+----------+----------+
'gallery_images' table:
+------------+----------+
| gallery_id | image_id |
+------------+----------+
| 1 | 1 |
| 1 | 2 |
| 2 | 3 |
| 3 | 1 |
| 4 | 1 |
+------------+----------+
What I'd like to get back, so I can say 'For this photoshoot, there are X images in total, and these images are featured in Y galleries:
+----+--------------+-------------+---------------+
| id | name | image_count | gallery_count |
+----+--------------+-------------+---------------+
| 3 | Final test | 1 | 1 |
| 2 | Another test | 0 | 0 |
| 1 | Test shoot | 2 | 4 |
+----+--------------+-------------+---------------+
I'm currently trying the SQL below, which appears to work correctly but only ever returns one row. I can't work out why this is happening. Curiously, the below also returns a row even when 'shoots' is empty.
SELECT shoots.id,
shoots.name,
COUNT(DISTINCT shoot_images.image_id) AS image_count,
COUNT(DISTINCT gallery_images.gallery_id) AS gallery_count
FROM shoots
LEFT JOIN shoot_images ON shoots.id=shoot_images.shoot_id
LEFT JOIN gallery_images ON shoot_images.image_id=gallery_images.image_id
ORDER BY shoots.id DESC
Thanks for taking the time to look at this :)
You are missing the GROUP BY clause:
SELECT
shoots.id,
shoots.name,
COUNT(DISTINCT shoot_images.image_id) AS image_count,
COUNT(DISTINCT gallery_images.gallery_id) AS gallery_count
FROM shoots
LEFT JOIN shoot_images ON shoots.id=shoot_images.shoot_id
LEFT JOIN gallery_images ON shoot_images.image_id=gallery_images.image_id
GROUP BY 1, 2 -- Added this line
ORDER BY shoots.id DESC
Note: The SQL standard allows GROUP BY to be given either column names or column numbers, so GROUP BY 1, 2 is equivalent to GROUP BY shoots.id, shoots.name in this case. There are many who consider this "bad coding practice" and advocate always using the column names, but I find it makes the code a lot more readable and maintainable and I've been writing SQL since before many users on this site were born, and it's never cause me a problem using this syntax.
FYI, the reason you were getting one row before, and not getting and error, is that in mysql, unlike any other database I know, you are allowed to omit the group by clause when using aggregating functions. In such cases, instead of throwing a syntax exception, mysql returns the first row for each unique combination of non-aggregate columns.
Although at first this may seem abhorrent to SQL purists, it can be incredibly handy!
You should look into the MySQL function group by.
I have a table with pairs of matching records that I query like this:
select id,name,amount,type from accounting_entries
where name like "%05" and amount != 0 order by name limit 10;
Results:
+------+----------------------+--------+-------+
| id | name | amount | type |
+------+----------------------+--------+-------+
| 786 | D-1194-838HELLUJP-05 | -5800 | DEBIT |
| 785 | D-1194-838HELLUJP-05 | -5800 | DEBIT |
| 5060 | D-1195-UOK4HS5POF-05 | -5000 | DEBIT |
| 5059 | D-1195-UOK4HS5POF-05 | -5000 | DEBIT |
| 246 | D-1196-0FUCJI66BX-05 | -7000 | DEBIT |
| 245 | D-1196-0FUCJI66BX-05 | -7000 | DEBIT |
| 9720 | D-1197-W2J0EC1BOB-05 | -6500 | DEBIT |
| 9719 | D-1197-W2J0EC1BOB-05 | -6500 | DEBIT |
| 2694 | D-1198-MFKIKHGW0S-05 | -5500 | DEBIT |
| 2693 | D-1198-MFKIKHGW0S-05 | -5500 | DEBIT |
+------+----------------------+--------+-------+
10 rows in set (0.01 sec)
I need to perform an update so that the resulting data will look like this:
+------+----------------------+--------+--------+
| id | name | amount | type |
+------+----------------------+--------+--------+
| 786 | D-1194-838HELLUJP-05 | -5800 | DEBIT |
| 785 | C-1194-838HELLUJP-05 | 5800 | CREDIT |
| 5060 | D-1195-UOK4HS5POF-05 | -5000 | DEBIT |
| 5059 | C-1195-UOK4HS5POF-05 | 5000 | CREDIT |
| 246 | D-1196-0FUCJI66BX-05 | -7000 | DEBIT |
| 245 | C-1196-0FUCJI66BX-05 | 7000 | CREDIT |
| 9720 | D-1197-W2J0EC1BOB-05 | -6500 | DEBIT |
| 9719 | C-1197-W2J0EC1BOB-05 | 6500 | CREDIT |
| 2694 | D-1198-MFKIKHGW0S-05 | -5500 | DEBIT |
| 2693 | C-1198-MFKIKHGW0S-05 | 5500 | CREDIT |
+------+----------------------+--------+--------+
10 rows in set (0.01 sec)
One entry should negate the other entry. It doesn't matter if I update the first or second matching record, what matters is that one has a positive amount and the other has a negative amount. And the type and name need to be updated.
Any clues on how to do this? What would the update command look like? Maybe using a group by clause? I have some ideas on how to do it with a stored procedure, but can I do it with a simple update?
Try this:
UPDATE accounting_entries as ae
SET name = 'C' + SubString(name, 1, Length(name) - 1))
amount = amount * -1
type = 'Credit'
WHERE id =
(SELECT MIN(id) FROM
(SELECT * FROM accounting_entries) as temp
GROUP BY name)
The key is the subquery in the WHERE section that limits the updates to the lowest ID of each name value. The assumption is that the lower ID is the one that you will always want to update. If this is not correct, then update the subquery based on whatever rule you would use.
Edit: Update to subquery based on technique found here, due to limitation on mysql defined here.
This query gives a method for updating all records at once (as it seemed like this is what the OP was looking for. However, the most efficient way to do this would be to enumerate through all records in code (php, asp.net, etc), and through code-based methods update the rows that needed to change. This would eliminate the performance issues inherent with running updates off of subqueries in mysql.
If the ID:s for a pair always match the formula x and x+1, you could say something like
WHERE MOD(`id`, 2) = 1
EDIT: I haven't tested this code, so I can't guarantee that it's possible to put a column name into a MOD like this, but it might be worth a try, and/or further investigation.
Does this constraint hold true all the time (D == -C) ?
If so, you do not need to keep redundant data in your table, store only one "amount" value (for example the debit):
786 | 1194-838HELLUJP-05 | -5800
and then, on the application level, append a D- to the name and get the raw amount or append a C- and get the - amount.