Use IF in mysql select query to change the WHERE clause - mysql

I need to create a select statement on a table like this:
id rank name city
34 0 adm TO
44 0 sas BA
44 1 wqe BS
92 0 adm TO
92 1 ter BO
92 2 ter BO
92 3 ter RM
what I want to select is to count the number of rows where rank is > 0 but only for ids that have more than one rank value. For those id that just have one record, thus rank is 0, then I want to pick that record. If I use:
SELECT id, count(rank) as t
FROM mytable
WHERE rank > 0
GROUP BY id
then, for instance, I omit id=34.
My optimal results set would be:
id t
34 1
44 1
92 3
Any hint on how to accomplish this task?


You can use something like the following:
SELECT id,
CASE
WHEN cntNonZero = 0 THEN cntZero
ELSE cntNonZero
END AS t
FROM (
SELECT id,
COUNT(CASE WHEN rank > 0 THEN 1 END) AS cntNonZero,
COUNT(CASE WHEN rank = 0 THEN 1 END) AS cntZero
FROM mytable
GROUP BY id ) s
Demo here

Related

How can I get the sum of a row using LIMIT

id
reg_No
Subj_id
sub_title
score
Class_id
1
98
23
MATHEMATICS
90
2
2
98
21
ENGLISH LANG
60
2
3
98
24
PHYSICS
78
2
4
98
23
CHEMISTRY
100
2
5
98
21
BIOLOGY
81
2
6
98
24
AGRICULTURE
87
2
I want to select the best SUM(score) of the four(4) subjects including English and mathematics.
It suppose to sum 90+60+100+87 = 337
But, it's summing the entire column
Here is my query
SELECT SUM(score)
FROM table1
WHERE reg_no = 98
AND class_id=2
ORDER BY CASE WHEN sub_title IN ('English Language','Mathematics')
THEN 0
ELSE 1 END, score DESC LIMIT 4

The priority of SELECT is higher than LIMIT, therefore, you have to use a subquery
SELECT sum(score)
FROM
(
SELECT *
FROM tab
WHERE reg_no = 98 AND class_id=2
ORDER BY CASE WHEN sub_title IN ('English Language','Mathematics')
THEN 0
ELSE 1 END, score DESC
LIMIT 4
) t
DEMO

An easy way to split into two queries. The first one gets the Math and English score values, and the second one gets the two highest scores from the remaining values.
SQL Server:
With CTE As (
Select Top 2 Score From table1 Where reg_no = 98 And class_id=2 And sub_title Not In ('MATHEMATICS','ENGLISH LANG')
Order by Score Desc
Union All
Select Score From table1 Where reg_no = 98 And class_id=2 And sub_title In ('MATHEMATICS','ENGLISH LANG')
)
Select Sum(Score)
From CTE
MySQL:
With CTE As (
Select Score
From
(Select Score From table1 Where reg_no = 98 And class_id=2 And sub_title Not In ('MATHEMATICS','ENGLISH LANG')
Order by Score Desc
Limit 2) As S
Union All
Select Score From table1 Where reg_no = 98 And class_id=2 And sub_title In ('MATHEMATICS','ENGLISH LANG')
)
Select Sum(Score)
From CTE

How to add a null value in the group_concat if the record does not exist?

I have this SQL query with substring_index and group_concat but the results I get does not give the right location of the values because the values does not exist.
I need to add a null or zero value in order to have the right location of the values in the sql result.
In the table there are three lid (1, 2, 3). The lid should be the basis count of the P's (P1, P2, P3) for the substring_index.
This is the table:
lid class_id class total
----- ------- ----- -----
1 73 Leader 10000
1 77 Consultant 8000
1 83 Coordinator 6000
2 73 Leader 20000
2 76 Staff 8000
2 77 Consultant 10000
3 73 Leader 30000
3 78 Team Leader 8000
This is the SQL query I used to group_concat for the totals and substring_index to separate the grouped values with their each column (P1, P2, P3)
SELECT *, GROUP_CONCAT(lid) as lids, GROUP_CONCAT(pyear) as pyears,
COUNT(DISTINCT lib_id) AS total_count,
CASE WHEN COUNT(*)>=1 THEN SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(if(total is null,0,total) ORDER BY lid ASC SEPARATOR ' '),' ',1),' ',-1) END AS P1,
CASE WHEN COUNT(*)>=2 THEN SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(if(total is null,0,total) ORDER BY lid ASC SEPARATOR ' '),' ',2),' ',-1) END AS P2,
CASE WHEN COUNT(*)>=3 THEN SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(if(total is null,0,total) ORDER BY lid ASC SEPARATOR ' '),' ',3),' ',-1) END AS P3
FROM (
SELECT * FROM view_items WHERE lid='1'
UNION
SELECT * FROM view_items WHERE lid='2'
UNION
SELECT * FROM view_items WHERE lid='3'
) AS AZ GROUP BY class_id
This is the result of the above query:
class id class lids P1 P2 P3
--------- ----- ----- ---- ---- ----
73 Leader 1,2,3 10000 20000 30000
76 Staff 2 8000
77 Consultant 1,2 8000 10000
78 Team Leader 3 8000
83 Coordinator 1 6000
The lids should always have three count even though the record does not exists, a zero or null value should be added. How to do the adding of null value?
This is the expected result I need.
class id class lids P1 P2 P3
--------- ----- ----- ---- ---- ----
73 Leader 1,2,3 10000 20000 30000
76 Staff 0,2,0 0 8000 0
77 Consultant 1,2,0 8000 10000 0
78 Team Leader 0,0,3 0 0 8000
83 Coordinator 1,0,0 6000 0 0

To get 0 values where no lid is present in the table, you need to generate a list of all lid values for all class_id values, which you can do with a CROSS JOIN of two SELECT DISTINCT queries (one for lid, one for class_id). This can then be LEFT JOINed to the table, to get the required total value for each P group using conditional aggregation:
SELECT c.class_id,
MAX(v.class),
GROUP_CONCAT(COALESCE(v.lid, 0) ORDER BY l.lid) AS lids,
MAX(CASE WHEN v.lid=1 THEN total ELSE 0 END) AS P1,
MAX(CASE WHEN v.lid=2 THEN total ELSE 0 END) AS P2,
MAX(CASE WHEN v.lid=3 THEN total ELSE 0 END) AS P3
FROM (SELECT DISTINCT lid FROM view_items) l
CROSS JOIN (SELECT DISTINCT class_id FROM view_items) c
LEFT JOIN view_items v ON v.lid = l.lid AND v.class_id = c.class_id
GROUP BY c.class_id
Output:
class_id class lids P1 P2 P3
73 Leader 1,2,3 10000 20000 30000
76 Staff 0,2,0 0 8000 0
77 Consultant 1,2,0 8000 10000 0
78 Team Leader 0,0,3 0 0 8000
83 Coordinator 1,0,0 6000 0 0
Demo on dbfiddle

Use else 0 in case expression
SELECT *, GROUP_CONCAT(lid) as lids, GROUP_CONCAT(pyear) as pyears,
COUNT(DISTINCT lib_id) AS total_count,
CASE WHEN COUNT(*)>=1 THEN SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(if(total is null,0,total) ORDER BY lid ASC SEPARATOR ' '),' ',1),' ',-1) else 0 END AS P1,
CASE WHEN COUNT(*)>=2 THEN SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(if(total is null,0,total) ORDER BY lid ASC SEPARATOR ' '),' ',2),' ',-1) else 0 END AS P2,
CASE WHEN COUNT(*)>=3 THEN SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(if(total is null,0,total) ORDER BY lid ASC SEPARATOR ' '),' ',3),' ',-1) else 0 END AS P3
FROM (
SELECT * FROM view_items WHERE lid='1'
UNION
SELECT * FROM view_items WHERE lid='2'
UNION
SELECT * FROM view_items WHERE lid='3'
) AS AZ GROUP BY class_id

I think the problem is, that you say count >= 1, but count >= 3 is also count >=1 so your code never reaches this line. You have to say,
CASE WHEN COUNT() >=1 AND COUNT () < 2...
CASE WHEN COUNT() >=2 AND COUNT () < 3...

I don't think GROUP_CONCAT() is the right approach for what you want. Try this:
SELECT vi.class_id, vi.class,
COUNT(DISTINCT vi.lib_id) AS total_count,
CONCAT_WS(',',
MAX(CASE WHEN vi.lid = 1 THEN 1 ELSE 0 END),
MAX(CASE WHEN vi.lid = 2 THEN 1 ELSE 0 END),
MAX(CASE WHEN vi.lid = 3 THEN 1 ELSE 0 END)
) as lids,
SUM(CASE WHEN vi.lid = 1 THEN vi.total ELSE 0 END) as total_1,
SUM(CASE WHEN vi.lid = 2 THEN vi.total ELSE 0 END) as total_2,
SUM(CASE WHEN vi.lid = 3 THEN vi.total ELSE 0 END) as total_3
FROM view_items vi
WHERE vi.lid IN (1, 2, 3)
GROUP BY vi.class_id;
Notes:
Your subquery and UNION are not needed. In MySQL, these can actually hurt performance.
I assume that lid is a number, so I've removed the single quotes.
You can use conditional aggregation for each of the totals that you want. Parsing GROUP_CONCAT() is not the right way to do this.
Your question is about the lids. The CONCAT_WS() does what you want -- concatenating either the value (if it appears) or zero if it does not.

MySQL: Get all rows if specific value reached after date

In MySQL, I want to find all the rows where the value of a column went to 0 after a specific date.
So, given the data:
cat value date
a 95 2015-09-01
a 78 2015-10-01
a 0 2015-11-01
a 0 2015-12-01
b 129 2015-09-01
b 230 2015-10-01
b 201 2015-11-01
b 140 2015-12-01
In this case, I want to run a query that asks:
Which categories have 0 value after 10/1/2015 and had a positive value before 11/1/2015?
The result should show category "a".
I suspect is a nested select statement, but haven't quite figured it out.

select * from yourTable where value = 0 and date > '2015-10-01' and cat in (
select distinct cat where value > 0 and date < '2015-11-1'
)
Explanation: you can split the query to two parts - the inner query with the in statement is in charge of getting the cat ID's that were positive before 11/1/15, and the where value = 0 and date > '2015-10-01' will give you those that are 0 after 10/1/15

Building off what Nir Levy said, if you only want the category to be returned, you can select just the distinct values for cat:
SELECT DISTINCT cat
FROM stack_test.your_table
WHERE value = 0 AND date > '2015-10-01' AND
cat IN (SELECT cat FROM stack_test.mysql_rows WHERE value > 0 AND date < '2015-11-01');

Selecting a count on two separate conditions

Let's say I have the following data.
id name_id completed
1 10 1
2 10 0
3 15 1
4 10 0
5 20 1
6 15 0
7 20 1
8 15 0
I'm trying to find a count by the name id, which is pretty simple
SELECT name_id, COUNT(*) FROM db
GROUP BY name_id
Now, I have a second component which I want to include in the query.
For name_id 10, I want to count just those values where completed is 1. For the other name_id's, I want to select them regardless of whether they are 0 or 1.
So I should end up with:
name_id count(*)
10 1
15 3
20 2
Name_id 10 only has a count of 1 because it's just the 1 which is completed, while the other counts include both 0 and 1.
Can anyone help with this task.
Thanks!

You can use a CASE expression inside of your aggregate function.
SELECT name_id,
sum(case
when name_id = 10
then case when completed = 1 then 1 else 0 end
else 1 end) Total
FROM db
GROUP BY name_id;
See SQL Fiddle with Demo.

Exclude the rows where name_id = 10 and completed = 0:
SELECT name_id, COUNT(*) FROM db
WHERE NOT (completed = 0 AND name_id = 10)
GROUP BY name_id

SELECT name_id, COUNT(*) FROM db
WHERE name_id != 10 or completed = 1
GROUP BY name_id

Count when name_id is not 10. If it is 10, count when completed = 1:
SELECT
name_id,
COUNT(CASE WHEN name_id <> 10 or completed = 1 THEN 1 END)
FROM db
GROUP BY name_id

MySQL query to count non-null values in a single row

I'm trying to put together a MYSQL query that will count the number of Non-Null (or better yet, non-zero) values in select fields in a single row and then sort from lowest to highest (based on the count). For example, I have a table with 5 fields... ID, Name, Score_1, Score_2, Score_3. I want to count how many times the value "0" exists in Score_1, Score_2 and Score_3 for each record, then sort from most non zero values to least.
ID Name Score_1 Score_2 Score_3
1 Dan 8 7 0
2 Joe 0 0 3
3 Chris 0 0 0
4 Mike 4 5 5
I assume the query has to look something like this...
Select ID, Name, Score_1, Score_2, Score_3 where (???) ORDER BY (???)
Output should look like this (ID 4 is displayed first since it has the least amount of non-zero entries)...
ID Name Score_1 Score_2 Score_3
4 Mike 4 5 5
1 Dan 8 7 0
2 Joe 0 0 3
3 Chris 0 0 0
I'm somewhat new to mysql query's, so any help would be greatly appreciated. I thought the COUNT function would help, but that function appears to count columns from all rows. Perhaps there is a way to use the COUNT function and limit it to a singel row so it can be sorted by that row count?

This should do what you want:
SELECT ID, Name, Score_1, Score_2, Score_3
FROM Table1
ORDER BY (Score_1 = 0) + (Score_2 = 0) + (Score_3 = 0)
Result:
ID Name Score_1 Score_2 Score_3
4 Mike 4 5 5
1 Dan 8 7 0
2 Joe 0 0 3
3 Chris 0 0 0

try This:
Select id, Count1, Count2, Count3, Count4
From
(Select
Sum(Case When IsNull(Score_1,0) = 0 Then 1 Else 0 End) Count1,
Sum(Case When IsNull(Score_2,0) = 0 Then 1 Else 0 End) Count2,
Sum(Case When IsNull(Score_3,0) = 0 Then 1 Else 0 End) Count3,
Sum(Case When IsNull(Score_4,0) = 0 Then 1 Else 0 End) Count4
From Table
Group By Id) Z -- This column (Id) better not be the PK for this table!!!
Order By Count1 + Count2 + Count3 + Count4