I'm having trouble with sorting out a query for the following:
Data:
Column1 Column2
2 0
0 -2
I'm trying to select the difference between Column1 and Column2, with a minimum of 0. Eg.
Row1=2
Row2=0
My current query is SELECT (Column1 - Column2) as total FROM blah.
I tried adding max(Column2, 0) into the query, but that just errors.
Try:
SELECT GREATEST(Column1 - Column2, 0)
from Table
The MySQL function MAX() is an aggregate function, often used in combination with a GROUP BY. It only takes one argument (the name of the column of which you want to select the maximum value). The GREATEST() function is the function you need (as Michael Pakhantsov pointed out).
Related
I run a SQL query like below in MySQL:
select *
from (
select 2 as o,1 as t from dual
union
select 1 as o,2 as t from dual
) x
order by if((select 1),o,t);
It works well, but when I use column relative position in if statement, it doesn't work.
How can I use column relative position in if in ORDER BY statement?
select *
from (
select 2 as o,1 as t from dual
union
select 1 as o,2 as t from dual
) x
order by if((select 0),1,2);
I'm not sure what your real confusion is. When an integer appears in an order by, then this is treated as a column number. Any other use of an integer is interpreted as an expression.
The use of column numbers has been removed from the SQL standard. Hence, its use in any particular database is not guaranteed in future releases. It is really better to use the column names.
I think you want to sort your query based on a criteria over two columns, if I'm correct, you can use something like this:
...
order by
case when (your criteria)
then column1
else column2
end;
Note: use union all instead union when you don't want to remove duplicate values as performance issue ;).
I want to calculate percentage for test groups.
I have group A,B and C. And I want to know how much success percentage each group have.
My first query is counting total test ran in each group by doing the following:
SELECT type, count(type) as total_runs
From mytable
Where ran_at > '2015-09-11'
Group by type
Second query is counting success for each group:
SELECT type, count(type) as success
FROM mytable
where run_status like '%success%' and ran_at> '2015-09-11'
Group by type
Now I need to divide one in the other and multiply in 100.
how do I do this in one query in an efficient way, I guess nested query is not so efficient- but anyway I can't see how I can uses nested query to solve it.
I would appreciate answer which include simple way, maybe not so efficient, and an efficient way with explanations
You can just use conditional aggregation:
SELECT type, sum(run_status like '%success%') as success,
100 * avg(run_status like '%success%') as p_success
FROM mytable
where ran_at> '2015-09-11'
Group by type;
In a numeric context, MySQL treats boolean expressions as integers with 1 for true and 0 for false. The above works assuming that run_status is not NULL. If it can be NULL, then you need an explicit case statement for the avg().
I had this one, but Gordon have a better solution if run_status is not NULL.
Select type, sum(if(run_status like '%success%',1,0)) / count(1) * 100) as p_success
From mytable
Where ran_at > '2015-09-11'
Group by type
I want to pass variable number parameters to sql query. As an example:
select column1
from Table
where column2 in ( '0080','0010')
group by column1
having count(distinct column2) >= 2
In the where clause, 2 arguments 0080 and 0010 are used. But this number of arguments can vary based on the input from user. As an example it could be like this:
select column1
from Table
where column2 in ( '0080','0010', '0020', '0050', '0060')
group by column1
having count(distinct column2) >= 5
So, this number of arguments is not fixed and it will be passed by the user from an .xml file.
How can we pass a variable number of arguments to the query? As the number of arguments is not fixed and it can be changed from time to time, can we use an array or something similar?
I would suggest you try to load the arguments into a temporary table and use that in the where clause in a subquery. In particular if your argument list becomes very large, this is much more scalable.
Say you have the following query:
SELECT * FROM table1 WHERE table1.id IN (1, 2, 3, 4, 5, ..., 999999)
What is a reasonable maximum for the number of items in the IN clause? I'm using Sphinx to generate full-text search results and inserting the IDs into a MySQL query. Is this an acceptable way to do it?
You can also have the IN clause take the results of a query, such as:
SELECT * FROM table1
WHERE table1.id IN
(
SELECT id from table2
)
That way, you don't need to generate a text string with all the possible values.
In mysql, you should be able to put as many values in the IN clause as you want, only constrained by the value of "max_allowed_packet".
http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#function_in
http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html#sysvar_max_allowed_packet
MariaDB (10.3.22 in my case) has a limit of 999 parameters to IN() before it creates a materialized temporary table, resulting in possibly much longer execution times. Depending on your indices. I haven't found a way to control this behaviour. MySQL 5.6.27 does not have this limit, at least not at ~1000 parameters. MySQL 5.7 might very well have the same "feature".
I ended up doing a series of where id = a or id = b ... but it also works fine by using series of where id in(a, b) or id in(c, d) ....
You have to add laravel row query and then add NOT IN condition into this:
$object->whereRaw('where id NOT IN (' . $array_list . ') ');
This will work for my code.
From my experience the maximum values is 1000 values in clause IN ('1',....,'1000'),
I have 1300 value in my excel sheet,I put them all into IN ,MySQL return only 1000 .
I have a statement that is:
ORDER BY IFNULL(rrp, wholesale) ASC
...but I wanted to know if there is a way to have an IFNULL statement that checks 3 or 4 or 5 columns? All from the same table.
Use COALESCE
e.g:
SELECT ....
FROM ....
ORDER BY COALESCE(rrp, wholesale, column3, column4)
You could chain them up, so the expression picks the first not-null value from a list of columns:
ORDER BY IFNULL(IFNULL(IFNULL(rrp, wholesale), some_column), some_other_column) ASC
Try using COALESCE; it may give you what you need.