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Create a user defined function that works with GROUP BY in mysql


Create a user defined function that works with GROUP BY in mysql

By : Xeno
Date : October 19 2020, 08:10 AM
should help you out User defined aggregate stored functions where added in MariaDB-10.3.3
MySQL can do aggregate functions however not in SQL. They need a [UDF (shared library implemenation)](https://dev.mysql.com/doc/refman/5.7/en/create-function-udf.html}
code :


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Using mysql user-defined variable with group by condition

Using mysql user-defined variable with group by condition


By : Gregory Sholl Santos
Date : March 29 2020, 07:55 AM
This might help you if I recall correctly, the problem here is that the value of the column that does not contain an aggregation function is computed when the first row of the group is processed, while the assignment @var:=SUM takes place when the aggregated value is computed.
That is you either need just to repeat the aggregation function in the other context, or if the aggregated function is rather complex, and you do not want to repeat: a) put everything in a subquery, b) use something like IF(COUNT(*), @var, @var) (which looks rather hacky)
How to create a Set of user-defined objects in Javascript with a user-defined equality function?

How to create a Set of user-defined objects in Javascript with a user-defined equality function?


By : sharanya dk
Date : March 29 2020, 07:55 AM
around this issue If you would accept to work with/override valueOf, then you could proceed like this:
code :
// Implementation of special Set:
function mySet() {
    var self = this;
    self.size = 0;
    // Use a private map that will be keyed by the valueOf() of each added item: 
    var map = new Map();
    self.add = function (item) {
        map.set(item.valueOf(), item);
        self.size = map.size;
    };
    self.has = function (item) {
        return map.has(item.valueOf());
    };
    self[Symbol.iterator] = function* () {
        for (var pair of map) {
            yield pair[1]; // return the item ( not the valueOf() in [0])
        }
    };
    // etc...
}

// Test code:
myClass = function(val){
                 var self = this;
                 self.val = val;
                 self.valueOf = function () { return self.val; }; 
           }

a = new myClass(1.0);
b = new myClass(2.0);
c = new myClass(2.0);

s = new mySet(); //does not have to be actual "Set"
s.add(a);
s.add(b);
s.add(c);

document.write('size: ' + s.size + '<br>');
document.write('has(a): ' + s.has(a) + '<br>');
document.write('has(b): ' + s.has(b) + '<br>');
document.write('has(c): ' + s.has(c) + '<br>');

for (item of s) {
    document.write('stored item: ' + JSON.stringify(item) + '<br>');
};
How to check that a user-defined function works in r?

How to check that a user-defined function works in r?


By : Kozzzx
Date : March 29 2020, 07:55 AM
I wish this help you Before we (meaning, at my workplace) release any code to our production environment we run through a series of testing procedures to make sure our code behaves the way we want it to. It usually involves several people with different perspectives on the code.
Ideally, such verification should start before you write any code. Some questions you should be able to answer are:
Why lambda function is not applicable in case of list comprehension, whereas some other user defined function works in t

Why lambda function is not applicable in case of list comprehension, whereas some other user defined function works in t


By : user2218852
Date : March 29 2020, 07:55 AM
Hope that helps I have changed my question a bit, I think my question was not clear before. Apologies!!! , Your difference is because
code :
lambda i: i*2 
func = lambda i: i*2 
print(func)
[(lambda x: x*2)(i)  for i in range(4) ]
[func(i)  for i in range(4) ]
Apache Drill: How to create a user defined function that works similar to JSON.parse available in Javascript?

Apache Drill: How to create a user defined function that works similar to JSON.parse available in Javascript?


By : Shinji
Date : March 29 2020, 07:55 AM
will help you You can write a Simple UDF, Parse the Input JSON and return String.
Here is the documentation on How to https://drill.apache.org/docs/develop-custom-functions-introduction/
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