In some stored procedures I see the following statement in where clause:
...
where
(#val1 is null or val = #val)
What does it mean?
I have used this before in a stored procedure when passing a variable that is used to filter the result set. The null value signifies that the parameter should not be used as a filter.
If #val1 is null, then the expression is true and the results are not filtered.
If #val1 is not null, then the results will be filtered and the val column must match the parameter.
Related
SELECT * FROM Entity e WHERE e.Status <> ANY(ARRAY[1,2,3]);
Here Status is a nullable integer column. Using the above query i am unable to fetch the records whose status value is NULL.
SELECT * FROM Entity e WHERE (e.Status is NULL OR e.Status = 4);
This query does the trick. Could someone explain me why the first query was not working as expected.
NULL kinda means "unknown", so the expressions
NULL = NULL
and
NULL != NULL
are neither true nor false, they're NULL. Because it is not known whether an "unknown" value is equal or unequal to another "unknown" value.
Since <> ANY uses an equality test, if the value searched in the array is NULL, then the result will be NULL.
So your second query is correct.
It is spelled out in the docs Array ANY:
If the array expression yields a null array, the result of ANY will be null. If the left-hand expression yields null, the result of ANY is ordinarily null (though a non-strict comparison operator could possibly yield a different result). Also, if the right-hand array contains any null elements and no true comparison result is obtained, the result of ANY will be null, not false (again, assuming a strict comparison operator). This is in accordance with SQL's normal rules for Boolean combinations of null values.
FYI:
e.Status is NULL OR e.Status = 4
can be shortened to:
e_status IS NOT DISTINCT FROM 4
per Comparison operators.
I have a requirement to load null if the total hours is less than previous total hours else the difference
iif(lesser(TOTAL_HOURS, PREVIOUS_TOTAL_HOURS),null(),TOTAL_HOURS-PREVIOUS_TOTAL_HOURS)
It gives me expression could not be evaluated.
Not all rows have values for these fields, some of them are null. They are numeric fields in database.
I just want to replace negative results with null
If you look at the document iif it says
iif(<condition> : boolean, <true_expression> : any, [<false_expression> : any]) => any
Based on a condition applies one value or the other. If other is
unspecified it is considered NULL. Both the values must be
compatible(numeric, string...).
Now as per your expression:
iif(lesser(TOTAL_HOURS, PREVIOUS_TOTAL_HOURS),null(),TOTAL_HOURS-PREVIOUS_TOTAL_HOURS)
since first value you have mentioned is of type null it expects TOTAL_HOURS-PREVIOUS_TOTAL_HOURS must also return a same type null
What you can try is:
iif(lesser(TOTAL_HOURS, PREVIOUS_TOTAL_HOURS),toInteger(null()),TOTAL_HOURS-PREVIOUS_TOTAL_HOURS)
OR
case(TOTAL_HOURS < PREVIOUS_TOTAL_HOURS, toInteger(null()), minus(TOTAL_HOURS,PREVIOUS_TOTAL_HOURS) )
original query looks like this :
UPDATE reponse_question_finale t1, reponse_question_finale t2 SET
t1.nb_question_repondu = (9-(ISNULL(t1.valeur_question_4)+ISNULL(t1.valeur_question_6)+ISNULL(t1.valeur_question_7)+ISNULL(t1.valeur_question_9))) WHERE t1.APPLICATION = t2.APPLICATION;
I know you cannot update 2 tables in a single query so i tried this :
UPDATE reponse_question_finale t1
SET nb_question_repondu = (9-(COALESCE(t1.valeur_question_4,'')::int+COALESCE(t1.valeur_question_6,'')::int+COALESCE(t1.valeur_question_7)::int+COALESCE(t1.valeur_question_9,'')::int))
WHERE t1.APPLICATION = t1.APPLICATION;
But this query gaves me an error : invalid input syntax for integer: ""
I saw that the Postgres equivalent to MySQL is COALESCE() so i think i'm on the good way here.
I also know you cannot add varchar to varchar so i tried to cast it to integer to do that. I'm not sure if i casted it correctly with parenthesis at the good place and regarding to error maybe i cannot cast to int with coalesce.
Last thing, i can certainly do a co-related sub-select to update my two tables but i'm a little lost at this point.
The output must be an integer matching the number of questions answered to a backup survey.
Any thoughts?
Thanks.
coalesce() returns the first non-null value from the list supplied. So, if the column value is null the expression COALESCE(t1.valeur_question_4,'') returns an empty string and that's why you get the error.
But it seems you want something completely different: you want check if the column is null (or empty) and then subtract a value if it is to count the number of non-null columns.
To return 1 if a value is not null or 0 if it isn't you can use:
(nullif(valeur_question_4, '') is null)::int
nullif returns null if the first value equals the second. The IS NULL condition returns a boolean (something that MySQL doesn't have) and that can be cast to an integer (where false will be cast to 0 and true to 1)
So the whole expression should be:
nb_question_repondu = 9 - (
(nullif(t1.valeur_question_4,'') is null)::int
+ (nullif(t1.valeur_question_6,'') is null)::int
+ (nullif(t1.valeur_question_7,'') is null)::int
+ (nullif(t1.valeur_question_9,'') is null)::int
)
Another option is to unpivot the columns and do a select on them in a sub-select:
update reponse_question_finale
set nb_question_repondu = (select count(*)
from (
values
(valeur_question_4),
(valeur_question_6),
(valeur_question_7),
(valeur_question_9)
) as t(q)
where nullif(trim(q),'') is not null);
Adding more columns to be considered is quite easy then, as you just need to add a single line to the values() clause
I want to filter out the output without rows containing null values or blank columns. I am using SQL Server 2012 there is no option named 'Blank' as in SS2005 where I can filter the rows. I also tried following expression but it gives me error or not showing correct output
=IsNothing(Fields!ABC.Value)!= True
=Fields!ABC.Value = ''
Please suggest the solution.
Pull up the tablix or group properties
Switch to "Filters"
Add a new filter
Set the expression to:
=IsNothing(Fields!YourFieldHere.Value)
Set the type to "Boolean" (see screenshot below) otherwise you'll get a "cannot compare data of types boolean and string" error.
Set the value to false
This works for filtering both rows and groups.
We should use the isNothing method in the Expression, change the Text to Boolean
and then Value will be "True"
for example:
Expression
=IsNothing(Fields!TestA.Value)<>True
(Expression type should be Boolean)
Operator
=
Value
=True
Edit the SQL query, so that it will not return NULL values in the column to group on, but let it return a dummy value; for example: ISNULL(columnA, 'dummy')
In the column group definition add a filter: ColumnA <> 'dummy'.
A database field named income_source is queried using:
SELECT * FROM table_name WHERE income_source LIKE "salaried%"
This retrieves income_source values with a "salaried" prefix. In iReport, the PrintWhenExpression value for the field is set as:
$F{income_source}.equals("Salaried")? Boolean.TRUE:Boolean.FALSE
Why does the report output differ from the SQL output?
There are a few problems:
The value "salaried%" in the SQL differs from the value of "Salaried" in the expression.
The value "salaried%" uses the % to match all text after the letter d.
There is a bit of redundancy in the PrintWhenExpression.
Try the following expression:
$F{income_source}.startsWith( "salaried" )
Or:
$F{income_source}.trim().toLowerCase().startsWith( "salaried" )
One of those should work. You will also want to ensure Blank when null is checked. Otherwise, the expression becomes:
$F{income_source} == null ? Boolean.FALSE :
$F{income_source}.trim().toLowerCase().startsWith( "salaried" )