问题
A table Jobs which have 2 column JobId, City when we save job a job location may be multiple city like below
-----------------------------
JobId City
-------------------------------
1 New York
2 New York , Ohio , Virginia
3 New York , Virginia
how i count jobid in perticular city like i want count of jobid in New York city i want result like
New York 3 Ohio 1 Virginia 2
回答1:
Your database is poorly designed and you are going to have a lot of trouble down the line.
Using the current structure you can get the count using the find_in_set function but that you should avoid .
Your table is as
create table test
(jobid int ,city varchar(100));
insert into test values
(1,'New York'),
(2,'New York, Ohio,Virginia'),
(3,'New York,Virginia');
Now to get the count you can use the following
select
count(*) as tot from test
where
find_in_set('Virginia',city) > 0;
As I mentioned this is a poor db design the ideal would be as
- first a job table with job details
- a location table containing all the locations
- and finally a table linking a job and a location
So it would look like
create table jobs (jobid int, name varchar(100));
insert into jobs values
(1,'PHP'),(2,'Mysql'),(3,'Oracle');
create table locations (id int, name varchar(100));
insert into locations values (1,'New York'),(2,'Ohio'),(3,'Virginia');
create table job_locations (id int, jobid int, location_id int);
insert into job_locations values
(1,1,1),(2,2,1),(3,2,2),(4,2,3),(5,3,1),(6,3,3);
Now getting the count and many more operations will be fairly easy
select
count(j.jobid) as tot
from jobs j
join job_locations jl on jl.jobid = j.jobid
join locations l on l.id = jl.location_id
where
l.name = 'Virginia'
For counting all the jobs per city and using the above schema it would very simple
select
l.name,
count(j.jobid) as tot
from jobs j
join job_locations jl on jl.jobid = j.jobid
join locations l on l.id = jl.location_id
group by l.name
DEMO
回答2:
SELECT
SUBSTRING_INDEX(SUBSTRING_INDEX(all_city, ',', num), ',', -1) AS one_city,
COUNT(*) AS cnt
FROM (
SELECT
GROUP_CONCAT(city separator ',') AS all_city,
LENGTH(GROUP_CONCAT(citySEPARATOR ',')) - LENGTH(REPLACE(GROUP_CONCAT(citySEPARATOR ','), ',', '')) + 1 AS count_city
FROM table_name
) t
JOIN numbers n
ON n.num <= t.count_city
GROUP BY one_city
ORDER BY cnt DESC;
for getting count of comma separated distinct value run above query but getting correct resulr you should use one more table **numbers** which have only one column num integer type and insert some values.
if you getting error during GROUP_CONCAT(city separator ',') AS all_city in this condition set a global variable " SET group_concat_max_len = 18446744073709547520; "
回答3:
SELECT COUNT(*) AS jobs
FROM Jobs
WHERE FIELD_IN_SET('New York') > 0
;
You should read about database normalization though. Having a comma separated list of values in a database table always has a 'smell', e.g. you can only check for a specific city name here and can't easily create a list of job counts for all cities referred to in the job table in one go ...
See e.g. http://en.wikipedia.org/wiki/Database_normalization for a start ...
回答4:
Make JobId and City column as joined primary key. This will make your life easier. Do not insert multiple cities separated by commas.
-------------------------------------------------
JobId City // Other columns
-------------------------------------------------
1 New York
2 New York
2 Ohio
2 Virginia
3 New York
3 Virginia
Now you make the query will be something like this
select city, count(jobid) FROM TABLE GROUP BY city // Result will be New York 3, Ohio 1 and Virginia 2
回答5:
Design your table as mentioned below. Each city name and Job Id in each row.
Job ID City Name
1 New York
2 New York
1 Seattle
Then use the query as mentioned in the below link.
SQL: How to get the count of each distinct value in a column?
回答6:
Try this query,
SELECT COUNT(jobid), city FROM TABLE where city like '%newyork%';
来源：https://stackoverflow.com/questions/27165243/get-count-of-different-values-in-comma-separated-row-in-mysql