I have a table with some data like
id group_id f1 f2 f3
1 1 a b
2 1 c
3 2 a c
How can i retrieve one row with group_id and count of rows for each field satisfying some textual condition?
Like that:
MY_MAGIC_SELECT(`f1`='a',`f3`='c');
must return
group_id f1 f2 f3
1 1 0 0
2 1 0 1
Using a sequence of SUM(CASE...) aggregate functions to represent each of your conditions should do it. The CASE returns a 0 or 1 if the condition is matched, and the SUM() adds the result. The GROUP BY is applied on the group_id.
SELECT
group_id
SUM(CASE WHEN f1 = 'a' THEN 1 ELSE 0 END) AS f1,
SUM(CASE WHEN f2 = 'b' THEN 1 ELSE 0 END) AS f2,
/* f3 = 'b' isn't in your "magic select" but here it is anyway... */
SUM(CASE WHEN f3 = 'c' THEN 1 ELSE 0 END) AS f3
FROM
yourtable
GROUP BY group_id
Specifically for MySQL, you don't need the CASE since the boolean expression f1 = 'a' will itself return a 1 or 0. So you can simplify it to the example below. This is not portable to any RDBMS, however.
SELECT
group_id
SUM(f1 = 'a') AS f1,
SUM(f2 = 'b') AS f2,
SUM(f3 = 'c') AS f3
FROM
yourtable
GROUP BY group_id
Here is a quick demonstration on SQLfiddle.com
Well, it is simple MySQL and you need to learn this. Please check this out:
http://www.w3schools.com/sql/sql_where.asp
http://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html
SELECT column_name(s)
FROM table_name
WHERE column_name operator value
for example
SELECT * FROM Persons
WHERE City='Sandnes'
Related
I have a table like this
NAME FLAG
---------------------------
abc 1
abc 0
abc 2
def 1
def 2
xyz 0
xyz 0
xyz 1
efg 1
I need query that list the name (group the result) which flag not included 0 and included 1.The result simply like below:-
NAME FLAG
------------------
def 1
efg 1
I have tried the query but not results the same.
select * mytable where FLAG NOT IN (0) GROUP BY NAME;
This is the simplest solution I can come up with. I believe there are more elegant answers possible.
SELECT *
FROM mytable
WHERE name NOT IN (SELECT name FROM mytable WHERE flag = 0)
AND flag = 1;
You can use NOT EXISTS clause in this way.
select a.*
from tbl a
where not exists
(select *
from tbl b
where b.name=a.name
and b.flag=0)
and a.flag=1;
We can use aggregation. The trick is to run a condition on each row, and then use an aggregate function to pick out the net result of the condition from all of the rows...
SELECT t.name
FROM a_table_like_this t
GROUP BY t.name
HAVING MAX(t.flag=0) <> 1
AND MAX(t.flag=1) = 1
The expressions in the HAVING clause are MySQL shorthand.
A more ANSI standards compliant equivalent would be:
SELECT t.name
FROM a_table_like_this t
GROUP BY t.name
HAVING MAX( CASE WHEN t.flag=0 THEN 1 ELSE 0 END) <> 1
AND MAX( CASE WHEN t.flag=1 THEN 1 ELSE 0 END) = 1
To get a better handle on what this is doing, take a look at how those expressions are evaluated on each row. Remove the GROUP BY clause, and move those expressions into the SELECT list...
SELECT t.name
, t.flag
, CASE WHEN t.flag=0 THEN 1 ELSE 0 END AS `fl=0`
, CASE WHEN t.flag=1 THEN 1 ELSE 0 END AS `fl=1`
FROM a_table_like_this t
ORDER
BY t.name
, t.flag
We get something like
name flag fl=0 fl=1
------ ---- ---- ----
abc 1 0 1
abc 0 1 0
abc 2 0 0
def 1 0 1
def 2 0 0
xyz 0 1 0
xyz 0 1 0
xyz 1 0 1
efg 1 0 1
If we now aggregate these rows by name (GROUP BY name), we can use MAX() aggregate to pick out a 1 (if there's one in the group. Otherwise, we'll get back a 0.)
And we can do conditional tests on the results of aggregates functions in the HAVING clause.
I Have below mentioned table:
Where Val column has 3 distinct value a,b & c.
ID Val
1 a
1 a
1 b
2 b
2 c
2 c
3 c
I want to get count of unique ids and count of ids for respective Val value (i.e a,b & c).
I am using query like this but it helps me to identify count for a single Val value at a time.
SELECT ID,COUNT(*)
FROM table1
WHERE Val='c' GROUP BY ID;
Required output:
ID count a b c
1 3 2 1 0
2 3 0 1 2
3 1 0 0 1
You can use group by and sum the count when val is equal to a,b or c. See below:
select id,
count(*) as `count`,
sum(case when val = 'a' then 1 else 0 end) as a,
sum(case when val = 'b' then 1 else 0 end) as b,
sum(case when val = 'c' then 1 else 0 end) as c
from yourTable
group by id;
Just use conditional aggregation:
select id, count(*), sum(val = 'a') as a, sum(val = 'b') as b, sum(val = 'c') as c
from table1
group by id;
I have a table:
id flag
1 Y
1 Y
1 Y
1 N
1 N
2 Y
2 N
2 N
3 Y
3 N
i want to do as select statement which will give me the following output.
id count_flag_Y count_flag_N
1 3 2
2 1 2
3 1 1
I was trying using the select case method but getting syntax error.
SELECT id,SUM(CASE WHEN flag= 'Y') as count_flag_Y,
SUM(CASE WHEN flag= 'N') as count_flag_N
from tablename
GROUP BY id
Is there any way to do it?
Your query was not far off, you only have a slight problem with the CASE expressions. Try this:
SELECT id,
SUM(CASE WHEN flag= 'Y' THEN 1 ELSE 0 END) AS count_flag_Y,
SUM(CASE WHEN flag= 'N' THEN 1 ELSE 0 END) AS count_flag_N
FROM tablename
GROUP BY id
You are very close, but in MySQL the CASE is not needed:
SELECT id, SUM(flag = 'Y') as count_flag_Y,
SUM(flag = 'N') as count_flag_N
FROM tablename
GROUP BY id;
MySQL treats boolean expressions like integers in a numeric context, with "1" for true and "0" for false.
t_no name value
1 a 45
1 b 23
1 c 5
1 a 12
1 b 99
1 c 6
I need to show my above table as
no name value1 value2
1 a 45 12
1 b 23 99
1 c 5 6
You can't create dynamic columns in mysql alone, either in scripting language, or you can use group_concat to have them in one column:
SELECT to_no, name, GROUP_CONCAT(value)
FROM table GROUP BY to_no, name
result:
no name value
1 a 45,12
1 b 23,99
1 c 5,6
MySQL does not have a pivot function, but you can use an aggregate function with a CASE expression. Since you have multiple values for each t_no and name, then you could use user defined variables to assign a row number to each group of values:
select t_no, name,
max(case when rn=1 then value end) value1,
max(case when rn=2 then value end) value2
from
(
select t_no, name, value,
#rn:=case when #prev=t_no and #c=name then #rn else 0 end +1 rn,
#prev:=t_no,
#c:=name
from yourtable
cross join (select #rn:=0, #prev:=0, #c:=null) c
order by t_no, name
) d
group by t_no, name
order by t_no, name;
See SQL Fiddle with Demo
I've got a query that produces the right result, its just very slow. I feel like there must be a better way (perhaps without subqueries).
Table, result and query are below. I've anonymized the data and I have 8 subqueries rather than 2, but the format is the same.
Table "a":
id userId type amount
------------------------------------
1 1 a 400
2 1 b 300
3 1 c 230
4 2 a 600
5 2 b 500
6 2 c 430
I've got an index on each column and one additional one that encompasses the userId and type columns. I can also guarantee you that userId and type are unique (i.e. there would't be two type 'a' for user 1).
Desired Result:
userId typeAtotal typeBtotal
--------------------------------
1 400 300
2 600 500
My Query:
SELECT userId,
(SELECT amount
FROM a AS a2
WHERE a2.userId = a1.userId
AND a2.type = 'a') AS aAmt,
(SELECT amount
FROM a AS a3
WHERE a3.userId = a1.userId
AND a3.type = 'b') AS bAmt
FROM a AS a1
WHERE type IN ('a','b')
GROUP BY userId
Use:
SELECT t.userid,
MAX(CASE WHEN t.type = 'a' THEN amount ELSE NULL END) AS typeAtotal,
MAX(CASE WHEN t.type = 'b' THEN amount ELSE NULL END) AS typeBtotal
FROM YOUR_TABLE t
GROUP BY t.userid
If there can be more than one amount for either type - this will return the highest. If you want such situations added, use SUM:
SELECT t.userid,
SUM(CASE WHEN t.type = 'a' THEN amount ELSE NULL END) AS typeAtotal,
SUM(CASE WHEN t.type = 'b' THEN amount ELSE NULL END) AS typeBtotal
FROM YOUR_TABLE t
GROUP BY t.userid
Looks like cross-tabulation to me. You might try something like this:
SELECT userId,
SUM(IF(a.type = 'a'), a.amount, 0) AS aAmount,
SUM(IF(a.type = 'b'), a.amount, 0) AS bAmount
FROM a
WHERE type IN ('a', 'b')
GROUP BY a.userId
You might want to read this rather well-written tutorial: http://dev.mysql.com/tech-resources/articles/wizard/index.html
Edit: fixed the ELSE condition.