I have a column in one of my table where I store multiple ids seperated by comma's.
Is there a way in which I can use this column's value in the "IN" clause of a query.
The column(city) has values like 6,7,8,16,21,2
I need to use as
select * from table where e_ID in (Select city from locations where e_Id=?)
I am satisfied with Crozin's answer, but I am open to suggestions, views and options.
Feel free to share your views.
Building on the FIND_IN_SET() example from #Jeremy Smith, you can do it with a join so you don't have to run a subquery.
SELECT * FROM table t
JOIN locations l ON FIND_IN_SET(t.e_ID, l.city) > 0
WHERE l.e_ID = ?
This is known to perform very poorly, since it has to do table-scans, evaluating the FIND_IN_SET() function for every combination of rows in table and locations. It cannot make use of an index, and there's no way to improve it.
I know you said you are trying to make the best of a bad database design, but you must understand just how drastically bad this is.
Explanation: Suppose I were to ask you to look up everyone in a telephone book whose first, middle, or last initial is "J." There's no way the sorted order of the book helps in this case, since you have to scan every single page anyway.
The LIKE solution given by #fthiella has a similar problem with regards to performance. It cannot be indexed.
Also see my answer to Is storing a delimited list in a database column really that bad? for other pitfalls of this way of storing denormalized data.
If you can create a supplementary table to store an index, you can map the locations to each entry in the city list:
CREATE TABLE location2city (
location INT,
city INT,
PRIMARY KEY (location, city)
);
Assuming you have a lookup table for all possible cities (not just those mentioned in the table) you can bear the inefficiency one time to produce the mapping:
INSERT INTO location2city (location, city)
SELECT l.e_ID, c.e_ID FROM cities c JOIN locations l
ON FIND_IN_SET(c.e_ID, l.city) > 0;
Now you can run a much more efficient query to find entries in your table:
SELECT * FROM location2city l
JOIN table t ON t.e_ID = l.city
WHERE l.e_ID = ?;
This can make use of an index. Now you just need to take care that any INSERT/UPDATE/DELETE of rows in locations also inserts the corresponding mapping rows in location2city.
From MySQL's point of view you're not storing multiple ids separated by comma - you're storing a text value, which has the exact same meaing as "Hello World" or "I like cakes!" - i.e. it doesn't have any meaing.
What you have to do is to create a separated table that will link two objects from the database together. Read more about many-to-many or one-to-many (depending on your requirements) relationships in SQL-based databases.
Rather than use IN on your query, use FIND_IN_SET (docs):
SELECT * FROM table
WHERE 0 < FIND_IN_SET(e_ID, (
SELECT city FROM locations WHERE e_ID=?))
The usual caveats about first form normalization apply (the database shouldn't store multiple values in a single column), but if you're stuck with it, then the above statement should help.
This does not use IN clause, but it should do what you need:
Select *
from table
where
CONCAT(',', (Select city from locations where e_Id=?), ',')
LIKE
CONCAT('%,', e_ID, ',%')
but you have to make sure that e_ID does not contain any commas or any jolly character.
e.g.
CONCAT(',', '6,7,8,16,21,2', ',') returns ',6,7,8,16,21,2,'
e_ID=1 --> ',6,7,8,16,21,2,' LIKE '%,1,%' ? FALSE
e_ID=6 --> ',6,7,8,16,21,2,' LIKE '%,6,%' ? TRUE
e_ID=21 --> ',6,7,8,16,21,2,' LIKE '%,21,%' ? TRUE
e_ID=2 --> ',6,7,8,16,21,2,' LIKE '%,2,%' ? TRUE
e_ID=3 --> ',6,7,8,16,21,2,' LIKE '%,3,%' ? FALSE
etc.
Don't know if this is what you want to accomplish. With MySQL there is feature to concatenate values from a group GROUP_CONCAT
You can try something like this:
select * from table where e_ID in (Select GROUP_CONCAT(city SEPARATOR ',') from locations where e_Id=?)
this one in for oracle ..here string concatenation is done by wm_concat
select * from table where e_ID in (Select wm_concat(city) from locations where e_Id=?)
yes i agree with raheel shan .. in order put this "in" clause we need to make that column into row below code one do that job.
select * from table where to_char(e_ID)
in (
select substr(city,instr(city,',',1,rownum)+1,instr(city,',',1,rownum+1)-instr(city,',',1,rownum)-1) from
(
select ','||WM_CONCAT(city)||',' city,length(WM_CONCAT(city))-length(replace(WM_CONCAT(city),','))+1 CNT from locations where e_Id=? ) TST
,ALL_OBJECTS OBJ where TST.CNT>=rownum
) ;
you should use
FIND_IN_SET Returns position of value in string of comma-separated values
mysql> SELECT FIND_IN_SET('b','a,b,c,d');
-> 2
You need to "SPLIT" the city column values. It will be like:
SELECT *
FROM table
WHERE e_ID IN (SELECT TO_NUMBER(
SPLIT_STR(city /*string*/
, ',' /*delimiter*/
, 1 /*start_position*/
)
)
FROM locations);
You can read more about the MySQL split_str function here: http://blog.fedecarg.com/2009/02/22/mysql-split-string-function/
Also, I have used the TO_NUMBER function of Oracle here. Please replace it with a proper MySQL function.
IN takes rows so taking comma seperated column for search will not do what you want but if you provide data like this ('1','2','3') this will work but you can not save data like this in your field whatever you insert in the column it will take the whole thing as a string.
You can create a prepared statement dynamically like this
set #sql = concat('select * from city where city_id in (',
(select cities from location where location_id = 3),
')');
prepare in_stmt from #sql;
execute in_stmt;
deallocate prepare in_stmt;
Ref: Use a comma-separated string in an IN () in MySQL
Recently I faced the same problem and this is how I resolved it.
It worked for me, hope this is what you were looking for.
select * from table_name t where (select (CONCAT(',',(Select city from locations l where l.e_Id=?),',')) as city_string) LIKE CONCAT('%,',t.e_ID,',%');
Example: It will look like this
select * from table_name t where ',6,7,8,16,21,2,' LIKE '%,2,%';
I have a varchar(255) field within a source table and the following contents:
50339 My great example
2020002 Next ID but different title
202020 Here we go
Now I am processing the data and do an insert select query on it. From this field I would need the INT number at the beginning of the field. IT IS followed by 2 spaces and a text with var length, this text is what I need as well but for another field. In General I want to to put text and ID in two fields which are now in one.
I tried to grab it like this:
SELECT STATUS REGEXP '^(/d{6,8}) ' FROM products_test WHERE STATUS is not null
But then I learned that in MySQL 5.x there are no regexp within the SELECT statement.
How could I seperate those values within a single select statment, so I can use it in my INSERT SELECT?
From the correct solution of user slaakso, resulted another related problem since somtimes the STATUS field is empty which then results in only one insert, but in case there is a value I split it into two fields. So the count does not match.
My case statement with his solution somehow contains a syntax problem:
CASE STATUS WHEN ''
THEN(
NULL,
NULL
)
ELSE(
cast(STATUS as unsigned),
substring(STATUS, locate(' ', STATUS)+3)
)
END
You can do following. Note that you need to treat the columns separately:
select
if(ifnull(status, '')!='', cast(status as unsigned), null),
if(ifnull(status, '')!='', substring(status, locate(' ', status)+2), null)
from products_test;
See db-fiddle
I am working on the sql query in which I want to sort the string on the basis of numbers.
I have one column (Column Name is Name) table in which there are multiple fields. On using ORDER BY NAME, it prints in the following way:
hello_world
hello_world10
hello_world11
hello_world12
hello_world13
hello_world14
hello_world15
hello_world4
hello_world5
For the above query, I have used ORDER BY NAME; but it doesn't seem to print on the basis of numbers.
Problem Statement:
I am wondering what sql query I need to write or what changes I need to make in my sql query above so that it prints everything on the basis of numbers, the o/p should be this:
hello_world
hello_world4
hello_world5
hello_world10
hello_world11
hello_world12
hello_world13
hello_world14
hello_world15
you want a numeric ordering, then you need to create a numeric value to order on.
currently you have strings.
if the pattern is true, then you can use a combination of string manipulation to trim off the first characters, which should leave only numbers, then use TO_NUMBER() to convert for the ordering
something like
select name
from mytable
order by to_number( replace( name, 'hello_world','' ))
I think the simplest solution for this particular case (where all the values have the same prefix) is:
order by length(name), name
Try this:
SELECT name,
CASE WHEN REGEXP_INSTR(name, '[0-9]') = 0 THEN 0
ELSE CAST(SUBSTR(name, REGEXP_INSTR(name, '[0-9]')) AS INT)
END AS progressive
FROM my_table
ORDER BY progressive;
we can order it using replace and cast methods.
I tried the following query
select Name, cast(REPLACE(Name, 'hello_world', '') as UNSIGNED ) as repl from Users order by repl;
To generage sample data
CREATE TABLE Users (
Name varchar(255) NOT NULL
);
insert into Users(Name) values
('hello_world'),
('hello_world4'),
('hello_world5'),
('hello_world10'),
('hello_world11'),
('hello_world12'),
('hello_world13'),
('hello_world14'),
('hello_world15')
;
EDIT
query without replaced column,
select City from Persons order by cast(REPLACE(City, 'hello_world', '') as UNSIGNED );
Though the question is about mysql.
I tried in sql server.
create table #t1 (id varchar(100));
insert into #t1 (id) values ('Pq1'),('pq3'),('pq2')
select * from #t
order by
CAST(SUBSTRING(id + '0', PATINDEX('%[0-9]%', id + '0'), LEN(id + '0')) AS INT)
I'm trying to INSERT INTO a table, and I know 2 ways:
Adding rows as values:
INSERT INTO db_example.tab_example (id,name,surname,group)
VALUES ('','Tom','Hanks','1');
or from another table:
INSERT INTO db_example.tab_example (id,name,surname)
SELECT ID,first_name,last_name FROM db_contacts.tab_mygroup;
but what if I want to insert some values from another table (the second way), and some values manually like a default value (the first way).
here's my try (it didn't work):
INSERT INTO db_example.tab_example (id,name,surname,group)
VALUES (
SELECT ID FROM db_contacts.tab_mygroup,
SELECT first_name FROM db_contacts.tab_mygroup,
SELECT last_name FROM db_contacts.tab_mygroup,
'1'
);
I thought of creating a VIEWtable and it might solve the problem, but I thought there might be someway to add both together.
Thank you guys! I hope I described well what I need :)
Just return the literal value from the SELECT statement; add an expression to the SELECT list. For example:
INSERT INTO db_example.tab_example (id,name,surname,group)
SELECT ID
, first_name
, last_name
, '1' AS group
FROM db_contacts.tab_mygroup;
FOLLOWUP
Q: can I SELECT first_name and last_name in the same column using the AS function? or I need another function?
A: If you want to combine the values in the first_name and last_name into a single column, you could concatenate them using an expression, and use that expression in the SELECT list, e.g
CONCAT(last_name,', ',first_name')
or
CONCAT(first_name,' ',last_name)
The AS keyword won't have any effect in the context of an INSERT ... SELECT, but assigning an alias to that expression that matches the name of the column the expression is being inserted into does serve as an aid for the future reader.
INSERT INTO db_example.tab_example (id,name,surname,group,full_name)
SELECT ID
, first_name
, last_name
, '1' AS group
, CONCAT(first_name,' ',last_name) AS full_name
FROM db_contacts.tab_mygroup
Try this
INSERT INTO db_example.tab_example (id,name,surname)
SELECT id,first_name,'M. Nega'
FROM db_contacts.tab_mygroup
You can use join in the FROM clause. It should work!
I am using MySQL and have a table (documentShips) that I want to store connections / links between documents and users.
The users table has columns including id, first_name and last_name etc...
The documents table has columns including id and users, where the users column contains a comma separated value
E.g. "Joe Bloggs, Fred Nerk, Simon McCool" etc...
I want to match users between the tables (documents and users) using a like statement, e.g.:
where documents.authors like '% users.last_name %'
and insert them into the documentShips table, e.g.:
insert into documentShips (user_id, document_id) ... values () ... where ...
I am struggling to create a valid (mysql) insert statement to do this.
Any help would be greatly appreciated !!!
Thanks,
Jon.
If I understand correctly you can use FIND_IN_SET() like this
INSERT INTO documentShips (user_id, document_id)
SELECT u.id, d.id
FROM documents d JOIN users u
ON FIND_IN_SET(CONCAT(u.first_name, ' ', u.last_name), d.authors) > 0
ORDER BY d.id, u.id
Here is SQLFiddle demo
In order for it to work correctly you have to make sure that comma separated values in document.authors have no spaces before or after commas. If in fact you have spaces then eliminate them first with a query like this
UPDATE documents
SET authors = REPLACE(REPLACE(authors, ' ,', ','), ', ', ',');
Here is SQLFiddle demo
Now consider to normalize your documents table.
Use INSERT...SELECT syntax as shown in the MySQL documentation. The documentation also has some examples.