If the email column is NULL, I want to have the phone number value in the PRIMARY_Contact column. I am using CASE expression, but could not do it properly.
You may be looking for COALESCE. It will return the first non-null value from a selection. It's actually just shorthand for CASE, but may be easier for you to implement.
In your example, perhaps that would look like this:
SELECT COALESCE(EMAIL,PRIMARY_CONTACT)
Check out https://msdn.microsoft.com/en-us/library/ms190349.aspx for more details.
Related
I frequently find myself replacing values in columns using
when($"myCol".isNull,myCrazyFunction).otherwise($"myCol")
To me the .otherwise($"myCol") feels kind of redundant.
Is there a better way to replace some values under some condition and otherwise just leave everything as it is without using the otherwise?
I think you can use coalesce() for that.
select(coalesce($"myCol", myCrazyFunction))
Just remember that myCrazyFunction should return a Column type.
I store the following rows in my table ('DataScreen') under a JSONB column ('Results')
{"Id":11,"Product":"Google Chrome","Handle":3091,"Description":"Google Chrome"}
{"Id":111,"Product":"Microsoft Sql","Handle":3092,"Description":"Microsoft Sql"}
{"Id":22,"Product":"Microsoft OneNote","Handle":3093,"Description":"Microsoft OneNote"}
{"Id":222,"Product":"Microsoft OneDrive","Handle":3094,"Description":"Microsoft OneDrive"}
Here, In this JSON objects "Id" amd "Handle" are integer properties and other being string properties.
When I query my table like below
Select Results->>'Id' From DataScreen
order by Results->>'Id' ASC
I get the improper results because PostgreSql treats everything as a text column and hence does the ordering according to the text, and not as integer.
Hence it gives the result as
11,111,22,222
instead of
11,22,111,222.
I don't want to use explicit casting to retrieve like below
Select Results->>'Id' From DataScreen order by CAST(Results->>'Id' AS INT) ASC
because I will not be sure of the datatype of the column due to the fact that JSON structure will be dynamic and the keys and values may change next time. and Hence could happen the same with another JSON that has Integer and string keys.
I want something so that Integers in Json structure of JSONB column are treated as integers only and not as texts (string).
How do I write my query so that Id And Handle are retrieved as Integer Values and not as strings , without explicit casting?
I think your assumtions about the id field don't make sense. You said,
(a) Either id contains integers only or
(b) it contains strings and integers.
I'd say,
If (a) then numerical ordering is correct.
If (b) then lexical ordering is correct.
But if (a) for some time and then (b) then the correct order changes, too. And that doesn't make sense. Imagine:
For the current database you expect the order 11,22,111,222. Then you add a row
{"Id":"aa","Product":"Microsoft OneDrive","Handle":3095,"Description":"Microsoft OneDrive"}
and suddenly the correct order of the other rows changes to 11,111,22,222,aa. That sudden change is what bothers me.
So I would either expect a lexical ordering ab intio, or restrict my id field to integers and use explicit casting.
Every other option I can think of is just not practical. You could, for example, create a custom < and > implementation for your id field which results in 11,111,22,222,aa. ("Order all integers by numerical value and all strings by lexical order and put all integers before the strings").
But that is a lot of work (it involves a custom data type, a custom cast function and a custom operator function) and yields some counterintuitive results, e.g. 11,111,22,222,0a,1a,2a,aa (note the position of 0a and so on. They come after 222).
Hope, that helps ;)
If Id always integer you can cast it in select part and just use ORDER BY 1:
select (Results->>'Id')::int From DataScreen order by 1 ASC
In my frontend application I have a function that is called pick(VALUE,'col1','col2','col3'). If the VALUE is 2 the value in col2 should be picked.
This is very handsome for replacing long code using "case when", "switch case" or "if else" calculations.
I have tried to find a similar function in Postgres, but no luck so far. Seen some function array() and values() mentioned, but cannot find the correct syntax.
The goal is to set an return on of three column values depending on first column value.
Pseudo code (not working):
Select status values(column1,column2,column3)from code
I know I can do this by using "case-when-then-else-end", but I am looking for a shorter way to achieve the same thing.
Jsfiddle showing the principe. But I only want to pick ONE value depending on type:
http://sqlfiddle.com/#!15/e0b41/10
You can create an array of values from pr_* columns, then pick one of them in this way:
(array[prl_1,prl_2,prl_3])[code_type]
Here is a simple demo: http://sqlfiddle.com/#!15/e0b41/23
select *,
(array[prl_1,prl_2,prl_3])[code_type]
from code
left join prl on prl_id =1
Given this perl DBI query:
$qh = $db_connection->prepare ('SELECT addresses.* from addresses WHERE 1');
The addresses table structure might change in the future, that is, some new columns may get inserted into it. So there's no guarantee which index number a particular column may get assigned to.
When I do a $qh->fetchrow_array, I want to be able to determine what the index number of a particular column is so I can check to see if it's empty. For example, I want to see if the mail_addr column is empty like so:
if (!$$row[$index_number]) {
do_something();
}
How can I determine what the value $index_number should be?
This can be determined via $sth->{NAME}. However, this situation is probably more appropriate for fetchrow_hashref which implements all the gluing of indices to field names you're looking for:
while ( my $row = $qh->fetchrow_hashref ) {
if (!$row->{mail_addr}) {
do_something();
}
}
Also consider the FetchHashKeyName attribute, fetchrow_hashref('NAME_lc'), or the $sth->{NAME_lc} attribute, which will guarantee the case of fieldnames presented by the DBI. Different SQL engines will normalize the identifier case differently, often depending on whether the identifier was quoted when declared.
Firstly, please don't use the $$row[$index_number] syntax. Anyone looking at your code will be expecting to see that written as $row->[$index_number].
You've worked out why SELECT * is a bad idea. So don't do that. List the specific columns that you are interested in - that way you can impose your own order (fetchrow_array returns columns in the order that they appear in the SELECT clause).
Alternatively, switch to one of the hash-based fetch methods like fetchrow_hashref.
But the best alternative would be to look at using DBIx::Class.
I have data like abc1, abc2, abcK. The result after sort should display like abcK, abc1, abc2.
Is there any way to achieve this?
Specify a different collating sequence, either by using ALTER SESSION to change the collating sequence for your entire session or by using NLSSORT to change the collating sequence for a single ORDER BY. For example,
SELECT *
FROM YOUR_TABLE
ORDER BY NLSSORT(YOUR_COLUMN, 'NLS_SORT=WEST_EUROPEAN')
will order letters before numbers. SQLFiddle here
Share and enjoy.
You could use a CASE expression in the ORDER BY clause.
For example,
order by
case when translate(column,'x0123456789','x') is null then 2
else 1
end, column;
The TRANSLATE would evaluate the pure strings as NULL. Thus, the case would return 2, else for all others, 1. Thus, any string having a number, i.e. alphanumeric values would be below the pure alphabets.