This question already has answers here:
How to resolve ambiguous column names when retrieving results?
(11 answers)
Closed 2 years ago.
I have some big tables which I need to combine into a single very large table, to form a single-page data export for a statistical package.
This is easy with INNER JOIN but the some of the tables have the same column names and these are being overwritten by each other when I fetch them as an array in PHP.
There are 4 tables being joined with 30-200 columns in each so there are far too many field names to manually include in the query with aliases, as would be the norm in this situation.
Here's the query:
SELECT * FROM logs
INNER JOIN logdetail ON logdetail.logID = logs.id
INNER JOIN clients ON clients.id = logs.clientID
INNER JOIN records ON records.id = logdetail.id
WHERE logs.userID=1
Is there any way around this? I don't actually mind what the column names are as long as I have the data so if I could prepend the table name to each field, that would do the trick.
I would create a view, your view would be comprised of your long query with aliases
Here is an example taken from the manual
mysql> CREATE TABLE t (qty INT, price INT);
mysql> INSERT INTO t VALUES(3, 50);
mysql> CREATE VIEW v AS SELECT qty, price, qty*price AS value FROM t;
mysql> SELECT * FROM v;
+------+-------+-------+
| qty | price | value |
+------+-------+-------+
| 3 | 50 | 150 |
+------+-------+-------+
This has always worked for me, unless you have one to many or some other relationship among these tables, which will duplicate records.
SELECT * FROM logs l
INNER JOIN logdetail ld ON ld.logID = l.id
INNER JOIN clients c ON c.id = l.clientID
INNER JOIN records r ON r.id = ld.id
WHERE l.userID=1
As andrew says you can also use a View to get this thing working which is much cooler.
I found a solution for this. Simply, fetch each duplicate column a second time, this time using an alias. This way, the overwritten values are selected again and aliased:
SELECT * FROM logs,
clients.name as clientName,
logs.name as logName,
etc...
INNER JOIN logdetail ON logdetail.logID = logs.id
INNER JOIN clients ON clients.id = logs.clientID
INNER JOIN records ON records.id = logdetail.id
WHERE logs.userID=1
Note: There is no need to do this for the final instance of the duplicate, because this column will not have been overwritten. So, in the example above, there is no need to include a line like records.name as recordName because, since there are no columns after it which have the same name, the record.name field was never overwritten and is already available in the name column.
Related
This question already has answers here:
MySQL Results as comma separated list
(4 answers)
Closed 4 years ago.
I have a PHP/MySQL scenario where I want to display a list of events but also show all users assigned to an event. In MySQL I have an events, eventusers and users tables.
I can SELECT event_id, event_name FROM events then loop through results in PHP and then SELECT user_id FROM eventusers WHERE event=[event_id] in each result loop to get that particular event's users.
I am wondering if there is way to do this in one single SQL query (and it's also performance decent) so I get data from the events table as well as all the user IDs attached to the event from the eventusers table. Something like:
event id | event name | Users from eventusers table
------------------------------------------
1 | Soccer match | 3,56,79
2 | Cycling | 46,77,88,126,78
You should make use of a JOIN statement, which merges your tables:
SELECT column_name(s)
FROM table1
INNER JOIN table2 ON table1.column_name = table2.column_name;
In your case, you should do something like:
SELECT event_name, user
FROM events
INNER JOIN eventusers
ON events.event_id = eventusers.event_id
I hope this is helpful for you
You can use the join function:
select * from
table1 JOIN table2
ON table1.pk=table2.fk
and then add the condition
where table1.column= something
however you need to have both tables joined with a column (.pk and .fk), in this case it could be the eventuserid
select * from
events JOIN eventusers
ON events.eventuserid=eventusers.userid
where event.id= [event_id]
Also you can subtitue the * with the columns you'll need: tablename.column and youll only get those column values in return
I'm sorry I dont understand the second part about the CSV file, can you clarify?
So, I have a table named clients, another one known as orders and other two, orders_type_a and orders_type_b.
What I'm trying to do is create a query that returns the list of all clients, and for each client it must return the number of orders based on this client's id and the amount of money this customer already spent.
And... I have no idea how to do that. I know the logic behind this, but can't find out how to translate it into a MySQL query.
I have a basic-to-thinkimgoodbutimnot knowledge of MySQL, but to this situation I've got really confused.
Here is a image to illustrate better the process I'm trying to do:
Useful extra information:
Each orders row have only one type (which is A or B)
Each orders row can have multiple orders_type_X (where X is A or B)
orders relate with client through the column client_id
orders_type_X relate with orders through the column order_id
This process is being made today by doing a query to retrieve clients, and then from each entry returned the code do another query (with php) to retrieve the orders and yet another one to retrieve the values. So basically for each row returned from the first query there is two others inside it. Needless to say that this is a horrible approach, the performance sucks and I thats the reason why I want to change it.
UPDATE width tables columns:
clients:
id | name | phone
orders:
id | client_id | date
orders_type_a:
id | order_id | number_of_items | price_of_single_item
orders_type_b:
id | order_id | number_of_shoes_11 | number_of_shoes_12 | number_of_shoes_13 | price_of_single_shoe
For any extra info needed, just ask.
If I understand you correctly, you are looking for something like this?
select c.*, SUM(oa.value) + SUM(ob.value) as total
from clients c
inner join orders o on c.order_id = o.id
inner join orders_type_a oa on oa.id = o.order_type_id AND o.type = 'A'
inner join orders_type_b ob on ob.id = o.order_type_id AND o.type = 'B'
group by c.id
I do not know your actual field names, but this returns the information on each customer plus a single field 'total' that contains the sum of the values of all the orders of both type A and type B. You might have to tweak the various names to get it to work, but does this get you in the right direction?
Erik's answer is on the right track. However, since there could be multiple orders_type_a and orders_type_b records for each order, it is a little more complex:
SELECT c.id, c.name, c.phone, SUM(x.total) as total
FROM clients c
INNER JOIN orders o
ON o.client_id = c.id
INNER JOIN (
SELECT order_id, SUM(number_of_items * price_of_single_item) as total
FROM orders_type_a
UNION ALL
SELECT order_id, SUM((number_of_shoes_11 + number_of_shoes_12 + number_of_shoes_13) * price_of_single_shoe) as total
FROM orders_type_b
) x
ON x.order_id = o.id
GROUP BY c.id
;
I'm making a few assumptions about how to calculate the total based on the columns in the orders_type_x tables.
How to show the common data from all table on base of vendorID where vendorID is unique key in my vendor table. and i use this as an foriegn key for all other(cost table, hour table,employee table, temporary table and ) table.
This is my Cost table struructre
This is my Hour table structure
This is my Temporarytable structure
This is my Employee table
This is my Final table vendor there are vendorID is unique Key
And i have use the following query but it is showing the different data.
SELECT * FROM cw_employee_csv as emp
inner join cw_cost_hour as cost on cost.vendorid=emp.vendorid
inner join cw_temp_employee as temp on cost.vendorid=temp.vendorid
inner join cw_hour_company as hour on temp.vendorid=hour.vendorid
inner join cw_vendor as vendor on temp.vendorid=vendor.vendorid
where vendor.companyid=1 ORDER BY hour.timeFrom ASC
If I understand, try this:
In your query in the field list explicit fields you want to show, for example:
SELECT
emp.assignmentid, cost.bill_type
FROM
cw_employee_csv AS emp
INNER JOIN
cw_cost_hour AS cost ON cost.vendorid = emp.vendorid
INNER JOIN
cw_temp_employee AS temp ON cost.vendorid = temp.vendorid
INNER JOIN
cw_hour_company AS hour ON temp.vendorid = hour.vendorid
INNER JOIN
cw_vendor AS vendor ON temp.vendorid = vendor.vendorid
WHERE
vendor.companyid = 1
ORDER BY
hour.timeFrom ASC
If the cardinality of tables is different and you want to show only one row per vendor, you must write a main query with cw_vendor and use some subquery to retrieve additional information by other table. Obviously, about parent table of your vendor table you can use INNER JOIN information without use subqueries.
EDIT AFTER COMMENT:
You start by this query (after chat discussion):
I extract an aggregate by company (I suppose to summarize your cost by vendor, if you want to apply another formula, it's the same algorithm)
select
sum(t.vendor_cost), t.companyid
from
(select
vendor.companyid as companyid, vendor.id as vendorid,
(select SUM(c.cost)
from cw_cost_hoyr c
where c.vendorid = vendor.id) as vendor_cost
from
cw_vendor vendor) as t
group by
t.companyid
Now we add other information but I must understand what do you want exactly with their relations
tbl_teams: team_id | team_name
tbl_players: player_id | player_fname | player_sname | player_bplace | player_bdate
tbl_players_stats: player_id | season_id | player_squad_no | team_id | player_apps | player_goals
Sorry if this is a basic question, but from all the MySQL tables and columns above I'd like to join the tables and then display the results by which season_id and team_id is selected. I need using PHP like this:
player_squad_no | player_sname, player_fname | team_name | player_apps | player_goals
I've looked at examples on here but still can't figure out how to write the MySQL query to do it with three separate tables and how to specify the table name before the column name. I've seen some examples with only the initial. tt.teams for instance. Is Left Join the way to do it?
Any help would be much appreciated.
With three separate tables, you simply write the join like this:
SELECT *
FROM Table_A AS A
LEFT JOIN Table_B AS B USING(ID)
LEFT JOIN Table_C AS C USING(ID)
Note that USING(column) is a syntactic alternative to ON A.column = B.column that you can use when the columns you want to join on have the same name in both tables.
In the above example, the tables are aliased with AS so that you can refer to them by the alias instead of the full table name. (AS is actually optional; you can just give the alias immediately after the table, if you're paying by the character.) Try to choose an alias that makes sense when you look at it; often times people will alias like this:
SELECT a.Name, b.State
FROM Customers AS a
LEFT JOIN Orders AS b
...etc.
But if you have a longer query, how are you supposed to remember what tables a and b refer to? At the very least, it would make sense to alias Customers AS C and Orders AS O; in some cases, I would go a step further: Registration AS REG, for instance. This gets more and more important as you JOIN more and more tables together.
Here's one way to write your query:
SELECT
Stats.player_squad_no,
CONCAT_WS(', ', Players.player_sname, Players.player_fname) AS player_full_name,
Teams.team_name,
Stats.player_apps,
Stats.player_goals
FROM tbl_players AS Players
LEFT JOIN tbl_players_stats AS Stats USING(player_id)
LEFT JOIN tbl_teams AS Teams USING(team_id)
The CONCAT_WS() function is included to assemble the player's full name the way you indicated you wanted it to be displayed. Since this function will output a column with a messy name, I also gave it an alias.
This should work
SELECT tbl_players_stats.player_squad_no,
tbl_players.player_sname,
tbl_players.player_fname,
tbl_teams.team_name,
tbl_players_stats.player_apps,
tbl_players_stats.player_goals
FROM tbl_players
JOIN tbl_players_stats ON tbl_players.player_id = tbl_players_stats.player_id
JOIN tbl_teams ON tbl_teams.team_id = tbl_players_stats.team_id
SELECT player_squad_no , player_sname, player_fname,team_name, player_apps, player_goals
FROM tbl_players_stats as s
JOIN tbl_players as p ON s.player_id=p.player_id
JOIN tbl_teams as t ON s.team_id=t.team_id
Nothing Joining is simple concept. But we should use proper columns for tables. While selecting the list of columns to select we should be little careful by using table aliasing. Try the below code
select c.player_squad_no,b.player_sname,b.player_fname,a.team_name,c.player_apps,c.player_goals
from tbl_teams a,tbl_players b,tbl_players_stats c
where a.team_id=c.team_id
and b.player_id=c.player_id
I have the following database structure:
Sites table
id | name | other_fields
Backups table
id | site_id | initiated_on(unix timestamp) | size(float) | status
So Backups table have a Many to One relationship with Sites table connected via site_id
And I would like to output the data in the following format
name | Latest initiated_on | status of the latest initiated_on row
And I have the following SQL query
SELECT *, `sites`.`id` as sid, SUM(`backups`.`size`) AS size
FROM (`sites`)
LEFT JOIN `backups` ON `sites`.`id` = `backups`.`site_id`
WHERE `sites`.`id` = '1'
GROUP BY `sites`.`id`
ORDER BY `backups`.`initiated_on` desc
The thing is, with the above query I can achieve what I am looking for, but the only problem is I don't get the latest initiated_on values.
So if I had 3 rows in backups with site_id=1, the query does not pick out the row with the highest value in initiated_on. It just picks out any row.
Please help, and
thanks in advance.
You should try:
SELECT sites.name, FROM_UNIXTIME(b.latest) as latest, b.size, b.status
FROM sites
LEFT JOIN
( SELECT bg.site_id, bg.latest, bg.sizesum AS size, bu.status
FROM
( SELECT site_id, MAX(initiated_on) as latest, SUM(size) as sizesum
FROM backups
GROUP BY site_id ) bg
JOIN backups bu
ON bu.initiated_on = bg.latest AND bu.site_id = bg.site_id
) b
ON sites.id = b.site_id
In the GROUP BY subquery - bg here, the only columns you can use for SELECT are columns that are either aggregated by a function or listed in the GROUP BY part.
http://dev.mysql.com/doc/refman/5.5/en/group-by-hidden-columns.html
Once you have all the aggregate values you need to join the result again to backups to find other values for the row with latest timestamp - b.
Finally join the result to the sites table to get names - or left join if you want to list all sites, even without a backup.
Try with this:
select S.name, B.initiated_on, B.status
from sites as S left join backups as B on S.id = B.site_id
where B.initiated_on =
(select max(initiated_on)
from backups
where site_id = S.id)
To get the latest time, you need to make a subquery like this:
SELECT sites.id as sid,
SUM(backups.size) AS size
latest.time AS latesttime
FROM sites AS sites
LEFT JOIN (SELECT site_id,
MAX(initiated_on) AS time
FROM backups
GROUP BY site_id) AS latest
ON latest.site_id = sites.id
LEFT JOIN backups
ON sites.id = backups.site_id
WHERE sites.id = 1
GROUP BY sites.id
ORDER BY backups.initiated_on desc
I have removed the SELECT * as this will only work using MySQL and is generally bad practice anyway. Non-MySQL RDBSs will throw an error if you include the other fields, even individually and you will need to make this query itself into a subquery and then do an INNER JOIN to the sites table to get the rest of the fields. This is because they will be trying to add all of them into the GROUP BY statement and this fails (or is at least very slow) if you have long text fields.