I've got this small assignment:
Find those rooms that have projectors, but not whiteboards.
CREATE TABLE Equipment
(
room VARCHAR(15),
type VARCHAR(20)
);
INSERT INTO Equipment VALUES ('Dreyer-201','projector');
INSERT INTO Equipment VALUES **('Zuse-127','projector');**
INSERT INTO Equipment VALUES ('Shannon-164','projector');
INSERT INTO Equipment VALUES ('Dreyer-201','whiteboard');
INSERT INTO Equipment VALUES **('Zuse-127','whiteboard');**
INSERT INTO Equipment VALUES ('Shannon-164','whiteboard');
This is my answer:
SELECT DISTINCT room, type
FROM Equipment
WHERE type = 'projector' AND NOT type = 'whiteboard'
And it is working - but my output lists the room Zuse-127. I know it stands alone with both projector and whiteboard, but how can I fix this problem? So the room Zuse-127 does not show.
Try this one use NOT IN() for the rooms which belongs to whiteboard
SELECT DISTINCT room, type
FROM Equipment
WHERE type = 'projector' AND room
NOT IN (SELECT `room` FROM Equipment WHERE type = 'whiteboard' )
A self-join is likely to perform much better than solutions using GROUP BY or subqueries.
SELECT e.room, e.type
FROM Equipment AS e
LEFT OUTER JOIN Equipment AS e2
ON e.room = e2.room AND e2.type = 'whiteboard'
WHERE e.type = 'projector'
AND e2.type IS NULL;
Put an index on (type,room) for best results.
Related
I have ~6 tables where I have to count or sum fields based on matching site_ids and date. I have the following query, with many subqueries which takes an extraordinary amount of time to run. I am certain there is an easier, more efficient way, however I am rather new to these more complex queries. I have read regarding optimizations, specifically using joins ON but struggling to understand and implement.
The goal is to speed this up and not bring my small server to it's knees when running. Any assistance or direction would be VERY much appreciated!
SELECT date(date_added) as dt_date,
site_id as dt_site_id,
(SELECT site_id from branch_mappings bm WHERE mark_id_site = dt.site_id) as site_id,
(SELECT parent_id from branch_mappings bm WHERE mark_id_site = dt.site_id) as main_site_id,
(SELECT corp_owned from branch_mappings bm WHERE mark_id_site = dt.site_id) as corp_owned,
count(id) as dt_calls,
(SELECT count(date_submitted) FROM mark_unbounce ub WHERE date(date_submitted) = dt_date AND ub.site_id = dt.site_id) as ub,
(SELECT count(timestamp) FROM mark_wordpress_contact wp WHERE date(timestamp) = dt_date AND wp.site_id = dt.site_id) as wp,
(SELECT count(added_on) FROM m_shrednations sn WHERE date(added_on) = dt_date AND sn.description = dt.site_id) as sn,
(SELECT sum(users) FROM mark_ga ga WHERE date(ga.date) = dt_date AND channel LIKE 'Organic%' AND ga.site_id = dt.site_id) as ga_organic
FROM mark_dialogtech dt
WHERE site_id is not null
GROUP BY site_name, dt_date
ORDER BY site_name, dt_date;
What you're doing is the equivalent of asking your server to query 7+ different tables every time you run this query. Personally, I use Joins and nested queries because I can whittle down do what I need.
The first 3 subqueries can be replaced with...
SELECT date(date_added) as dt_date,
dt.site_id as dt_site_id,
bm.site_id as site_id,
bm.parent_id as main_site_id,
bm.corp_owned as corp_owned,
FROM mark_dialogtech dt
INNER JOIN branch_mappings bm
ON bm.mark_id_site = dt.site_id
I'm not sure why you are running the last 3. Is there a business requirement? If so, consider how often this is to be run and when.
If absolutely necessary, add those to the joins like...
FROM mark_dialogtech dt
INNER JOIN
(SELECT site_id, count(date_submitted) FROM mark_unbounce GROUP BY site_id) ub
on ub.site_id = dt.site_id
This should limit the results to only records where the site_id exists in both the mark_dialogtech and mark_unbounce (or whatever table). From my experience, this method has sped things up.
Still, my concern is the number of aggregations you're performing. If they can be cached to a dashboard and pulled during slow times, that would be best.
Its hard to analyze how big is your query(no data examples) but in your case I hightly recommend to use CTE(Common Table Expressions). Check this :
https://www.sqlpedia.pl/cte-common-table-expressions/
CTEs do not have a physical representation in tempdb like temporary tables or tabular variables. CTE can be viewed as such a temporary, non-materialized view. When MSSQL executes a query and encounters a CTE, it replace the reference to that CTE with definition. Therefore, if the CTE data is used several times in a given query, the same code will be executed several times and MSSQL does not optimize it. Soo... it will work just for few data like you want to do.
Appreciate all the responses.
I ended up creating a python script to run the queries separately and inserting the results into the table for the respective KPI. So, I scrapped the idea of a single query due to performance. I concatenated each date and site_id to create the id, then leveraged an ON DUPLICATE KEY UPDATE with each INSERT statement.
The python dictionary looks like this, and I simply looped. Again, thanks for the help.
SELECT STATEMENTS (Python Dict)
"dt":"SELECT date(date_added) as dt_date, site_id as dt_site, count(site_id) as dt_count FROM mark_dialogtech WHERE site_id is not null GROUP BY dt_date, dt_site ORDER BY dt_date, dt_site;",
"ub":"SELECT date_submitted as ub_date, site_id as ub_site, count(site_id) as ub_count FROM mark_unbounce WHERE site_id is not null GROUP BY ub_date, ub_site;",
"wp":"SELECT date(timestamp) as wp_date, site_id as wp_site, count(site_id) as wp_count FROM mark_wordpress_contact WHERE site_id is not null GROUP BY wp_date, wp_site;",
"sn":"SELECT date(added_on) as sn_date, description as sn_site, count(description) as sn_count FROM m_shrednations WHERE description <> '' GROUP BY sn_date, sn_site;",
"ga":"SELECT date as ga_date, site_id as ga_site, sum(users) as ga_count FROM mark_ga WHERE users is not null GROUP BY ga_date, ga_site;"
INSERT STATEMENTS (Python Dict)
"dt":f"INSERT INTO mark_helper_rollup (id, on_date, site_id, dt_calls, added_on) VALUES ('{dbdata[0]}','{dbdata[1]}',{dbdata[2]},{dbdata[3]},'{dbdata[4]}') ON DUPLICATE KEY UPDATE dt_Calls={dbdata[3]}, added_on='{dbdata[4]}';",
"ub":f"INSERT INTO mark_helper_rollup (id, on_date, site_id, ub, added_on) VALUES ('{dbdata[0]}','{dbdata[1]}',{dbdata[2]},{dbdata[3]},'{dbdata[4]}') ON DUPLICATE KEY UPDATE ub={dbdata[3]}, added_on='{dbdata[4]}';",
"wp":f"INSERT INTO mark_helper_rollup (id, on_date, site_id, wp, added_on) VALUES ('{dbdata[0]}','{dbdata[1]}',{dbdata[2]},{dbdata[3]},'{dbdata[4]}') ON DUPLICATE KEY UPDATE wp={dbdata[3]}, added_on='{dbdata[4]}';",
"sn":f"INSERT INTO mark_helper_rollup (id, on_date, site_id, sn, added_on) VALUES ('{dbdata[0]}','{dbdata[1]}',{dbdata[2]},{dbdata[3]},'{dbdata[4]}') ON DUPLICATE KEY UPDATE sn={dbdata[3]}, added_on='{dbdata[4]}';",
"ga":f"INSERT INTO mark_helper_rollup (id, on_date, site_id, ga_organic, added_on) VALUES ('{dbdata[0]}','{dbdata[1]}',{dbdata[2]},{dbdata[3]},'{dbdata[4]}') ON DUPLICATE KEY UPDATE ga_organic={dbdata[3]}, added_on='{dbdata[4]}';",
It would be very difficult to analyze the query with out the data, Any ways!
try joining the tables and group it, that should improve the performance
here is a left join sample
SELECT column names
FROM table1
LEFT JOIN table2
ON table1.common_column = table2.common_column;
check this for more detailed inform https://learnsql.com/blog/how-to-left-join-multiple-tables/
I have two tables BOOKINGS and WORKER. Basically there is table for a worker and a table to keep track of what the worker has to do in a time frame aka booking. I’m trying to check if there is an available worker for a job, so I query the booking to check if requested time has available workers between the start end date. However, I get stuck on the next part. Which is returning the list of workers that do have that time available. I read that I could join the table passed on a shared column, so I tried doing an inner join with the WORKER_NAME column, but when I try to do this I get a ambiguous error. This leads me to believe I misunderstood the concept. Does anyone understand what I;m trying to do and knows how to do it, or knows why I have the error below. Thanks guys !!!!
CREATE TABLE WORKER (
ID INT NOT NULL AUTO_INCREMENT,
WORKER_NAME varchar(80) NOT NULL,
WORKER_CODE INT,
WORKER_WAGE INT,
PRIMARY KEY (ID)
)
CREATE TABLE BOOKING (
ID INT NOT NULL AUTO_INCREMENT,
WORKER_NAME varchar(80) NOT NULL,
START DATE NOT NULL,
END DATE NOT NULL,
PRIMARY KEY (ID)
)
query
SELECT *
FROM WORKERS
INNER JOIN BOOKING
ON WORKER_NAME = WORKER_NAME
WHERE (START NOT BETWEEN '2010-10-01' AND '2010-10-10')
ORDER BY ID
#1052 - Column 'WORKER_NAME' in on clause is ambiguous
In your query, the column "worker_name" exists in two tables; in this case, you must reference the tablename as part of the column identifer.
SELECT *
FROM WORKERS
INNER JOIN BOOKING
ON workers.WORKER_NAME = booking.WORKER_NAME
WHERE (START NOT BETWEEN '2010-10-01' AND '2010-10-10')
ORDER BY ID
In your query, the column WORKER_NAME and ID columns exists in both tables, where WORKER_NAME retains the same meaning and ID is re-purposed; in this case, you must either specify you are using WORKER_NAME as the join search condition or 'project away' (rename or omit) the duplicate ID problem.
Because the ID columns are AUTO_INCREMENT, I assume (hope!) they have no business meaning. Therefore, they could both be omitted, allowing a natural join that will cause duplicate columns to be 'projected away'. This is one of those situations where one wishes SQL had a WORKER ( ALL BUT ( ID ) ) type syntax; instead, one is required to do it longhand. It might be easier in the long run to to opt for a consistent naming convention and rename the columns to WORKER_ID and BOOKING_ID respectively.
You would also need to identify a business key to order on e.g. ( START, WORKER_NAME ):
SELECT *
FROM
( SELECT WORKER_NAME, WORKER_CODE, WORKER_WAGE FROM WORKER ) AS W
NATURAL JOIN
( SELECT WORKER_NAME, START, END FROM BOOKING ) AS B
WHERE ( START NOT BETWEEN '2010-10-01' AND '2010-10-10' )
ORDER BY START, WORKER_NAME;
This is good, but its returning the start and end times as well. I'm just wanting the WOKER ROWS. I cant take the start and end out, because then sql doesn’t recognize the where clause.
Two approaches spring to mind: push the where clause to the subquery:
SELECT *
FROM
( SELECT WORKER_NAME, WORKER_CODE, WORKER_WAGE FROM WORKER ) AS W
NATURAL JOIN
( SELECT WORKER_NAME, START, END
FROM BOOKING
WHERE START NOT BETWEEN '2010-10-01' AND '2010-10-10' ) AS B
ORDER BY START, WORKER_NAME;
Alternatively, replace SELECT * with a list of columns you want to SELECT:
SELECT WORKER_NAME, WORKER_CODE, WORKER_WAGE
FROM
( SELECT WORKER_NAME, WORKER_CODE, WORKER_WAGE FROM WORKER ) AS W
NATURAL JOIN
( SELECT WORKER_NAME, START, END FROM BOOKING ) AS B
WHERE START NOT BETWEEN '2010-10-01' AND '2010-10-10'
ORDER BY START, WORKER_NAME;
This error comes after you attempt to call a field which exists in both tables, therefore you should make a reference. For instance in example below I first say cod.coordinator so that DBMS know which coordinator I want
SELECT project__number, surname, firstname,cod.coordinator FROMcoordinatorsAS co JOIN hub_applicants AS ap ON co.project__number = ap.project_id JOIN coordinator_duties AS cod ON co.coordinator = cod.email
I have created three tables
CREATE TABLE guest(
name varchar(100),
ranking int,
PRIMARY KEY (name)
);
CREATE TABLE room(
roomname varchar(100),
wallcolor varchar(100),
rating int,
PRIMARY KEY(roomnane)
);
CREATE TABLE reservation(
name varchar(100),
roomname varchar(100),
day varchar(100),
moveinday int,
moveoutday int,
PRIMARY KEY(roomname, day, start, finish),
FOREIGN KEY(roomname) REFERENCES room(roomname),
FOREIGN KEY(name) REFERENCES guest(name)
);
I am trying to write a query to find the guests who reserved EVERY "LakeView" room
I tried the following
SELECT g.name
FROM guest g, reservation r, room rr
WHERE rr.name = g.name
AND rr.roomname = "LakeView"
GROUP BY g.name
This does not seem to list out every room. How could I gix this?
Input:
insert into guest values ('Andrew', 1);
insert into guest values ('Jack', 4);
insert into guest values ('Jake', 4);
insert into room values ('LakeView', 'white', 10);
insert into room values ('BayView', 'blue', 4);
insert into reservation values ('Andrew', 'LakeView', 'Friday', 10,15);
insert into reservation values ('Jake', 'LakeView', 'Monday', 10,16);
insert into reservation values ('Jack', ' BayView', 'Tuesday', 11,15);
Desired output is
Andrew
Jake
try this:
Solution 1:
SELECT
guest.name
FROM guest INNER JOIN
reservation ON reservation.name = guest.name
INNER JOIN room ON reservation.roomname = room.roomname
WHERE reservation.roomname = "LakeView"
GROUP BY guest.name
Here I've highlighted your mistakes:
You tried to match rr.name with g.name. That means you are
matching roomname with guest name which you didn't want (so far I
guess).
Another mistake is you are only checking "LakeView" only in room
table entries. So other guests who haven't reserved LakeView room
might appear in the final result set. You also need to filter those
records from reservation table which have LakeView roomname.
Here's your query modified based on the above observations:
Solution 2:
SELECT g.name
FROM guest g, reservation r, room rr
WHERE r.name = g.name
AND rr.roomname = "LakeView"
AND r.roomname = "LakeView"
GROUP BY g.name;
N:B: Solution 1 is encouraged to use. Try to avoid implicit joins which are stated in solution 2.
I personally think the INNER JOIN is better, because it is more
readable. It shows better the relations between the table. You got
those relations in the join, and you do the filtering in the WHERE
clause. This separation makes the query more readable.
Have a look at this post.
if you using php-mysql then it will be help
$qry=mysql_query("select name from reservation where roomname='LakeView'");
while($result=mysql_fetch_array($qry)
{
echo $result['name'];
}
I'm assuming that the 'name' column in the reservation table is the name of the guest or guests. If this is true it sounds like you only need the reservation table for the purposes of this query, but if you wanted to combine them all anyway:
select
rv.name as Guest
from room as r
left join reservation as rv on rv.roomname = r.roomname
left join guest as g on g.name = rv.name
where
rv.roomname = 'LakeView'
I can't seem to get this query right. I have tables like this (simplified):
person: PersonID, ...other stuff...
contact: ContactID, PersonID, ContactDate, ContactTypeID, Description
I want to get a list of all the people who had a contact of a certain type (or types) but none of another type(s) that occurred later. An easy-to-understand example: Checking for records of gifts received without having sent a thank-you card afterward. There might have been other previous thank-you cards sent (pertaining to other gifts), but if the most recent occurrence of a Gift Received (we'll say that's ContactTypeID=12) was not followed by a Thank You Sent (ContactTypeID=11), the PersonID should be in the result set. Another example: A mailing list would be made up of everyone who has opted in (12) without having opted out (11) more recently.
My attempt at a query is this:
SELECT person.PersonID FROM person
INNER JOIN (SELECT PersonID,ContactTypeID,MAX(ContactDate) FROM contact
WHERE ContactTypeID IN (12,11) GROUP BY PersonID) AS seq
ON person.PersonID=seq.PersonID
WHERE seq.ContactTypeID IN (12)`
It seems that the ContactTypeID returned in the subquery is for the last record entered in the table, regardless of which record has the max date. But I can't figure out how to fix it. Sorry if this has been asked before (almost everything has!), but I don't know what terms to search for.
Wow. A system to check who has been good and sent thank yous. I think I would be in your list...
Anyway. Give this a go. The idea is to create two views: the first with personId and the time of the most recently received gift and the second with personId and the most recently sent thanks. Join them together using a left outer join to ensure that people who have never sent a thank you are included and then add in a comparison between the most recently received time and the most recent thanks time to find impolite people:
select g.personId,
g.mostRecentGiftReceivedTime,
t.mostRecentThankYouTime
from
(
select p.personId,
max(ContactDate) as mostRecentGiftReceivedTime
from person p inner join contact c on p.personId = c.personId
where c.ContactTypeId = 12
group by p.personId
) g
left outer join
(
select p.personId,
max(ContactDate) as mostRecentThankYouTime
from person p inner join contact c on p.personId = c.personId
where c.ContactTypeId = 11
group by p.personId
) t on g.personId = t.personId
where t.mostRecentThankYouTime is null
or t.mostRecentThankYouTime < g.mostRecentGiftReceivedTime;
Here is the test data I used:
create table person (PersonID int unsigned not null primary key);
create table contact (
ContactID int unsigned not null primary key,
PersonID int unsigned not null,
ContactDate datetime not null,
ContactTypeId int unsigned not null,
Description varchar(50) default null
);
insert into person values (1);
insert into person values (2);
insert into person values (3);
insert into person values (4);
insert into contact values (1,1,'2013-05-01',12,'Person 1 Got a present');
insert into contact values (2,1,'2013-05-03',11,'Person 1 said "Thanks"');
insert into contact values (3,1,'2013-05-05',12,'Person 1 got another present. Lucky person 1.');
insert into contact values (4,2,'2013-05-01',11,'Person 2 said "Thanks". Not sure what for.');
insert into contact values (5,2,'2013-05-08',12,'Person 2 got a present.');
insert into contact values (6,3,'2013-04-25',12,'Person 3 Got a present');
insert into contact values (7,3,'2013-04-30',11,'Person 3 said "Thanks"');
insert into contact values (8,3,'2013-05-02',12,'Person 3 got another present. Lucky person 3.');
insert into contact values (9,3,'2013-05-05',11,'Person 3 said "Thanks" again.');
insert into contact values (10,4,'2013-04-30',12,'Person 4 got his first present');
An earlier data import in CiviCRM placed some member numbers into a custom field (member_number) instead of the more useful (external_id) field.
My (admittedly limited) SQL skills are way too rusty, but what I'm trying to do is:
IF external_id field is empty,
AND the contact_type is "Individual"
THEN copy the data from member_number to external_id for the matching internal id number.
I've tried a few variations of this, with different errors:
INSERT INTO test_table (external_id)
SELECT member_number
FROM member_info
INNER JOIN test_table
ON memberinfo.entity_id=test_table.id
WHERE test_table.external_id IS NULL AND test_table.contact_type = "Individual"
Do I even really need the INNER JOIN on this? And I know the WHERE statement usually refers to the table you're pulling from, not the one you're inserting to, but I can't remember the right way to do this.
update test_table
set external_id =
if(external_id = '' and contact_type = 'Individual', member_number,external_id)