i try to add but it returns blank as in field [Expr1]
Use Nz to add 0 (zero) for empty fields:
Expr1: Nz([F1],0)+Nz([F2],0)+Nz([F3],0)+Nz([F4],0)
You can use the Nz function to return zero, a zero-length string (" "), or another specified value when a Variant is Null. so try:
SELECT Nz(F1)+Nz(F2)+Nz(F3)+Nz(F4) AS Expr1
From [Table1]
Related
I am curious to know , how these queries work in database engine. Specially my focus is on line no 4 and 6.
1.SELECT * FROM tableName
2.SELECT * FROM tableName WHERE 1
3.SELECT * FROM tableName WHERE 123
4.SELECT * FROM tableName WHERE '2xyz'
5.SELECT * FROM tableName WHERE ''
6.SELECT * FROM tableName WHERE 'xyz'
In the above queries 1,2,3,4 are producing same result but 5 and 6 are not producing any result. why? what is diff b/w WHERE '2xyx' and 'xyz'?
How '2xyz' implicitly converted into 2 ?
The where clause evaluates to boolean true (not 0) or false (0) in order to decide if a record is in or out of the resultset.
Cases 2 and 3 retrive all records because the non zero numbers evaluate to true.
Case 3 retrieves all records because during the implicit string to number conversion mysql evaluates the string from left to right character by character. As long as as the characters can be evaluated as a number, mysql will take their value. This includes chopping of leading spaces, interpreting plus or minus signs, decimal points, and so on. So, the string '2xyx' is interpreted as 2, thus boolean true.
Case 4 and 5 do not retrieve any records because the strings' leftmost character cannot be evaluated as a number, so the conversion returns 0, thus boolean false.
Unfortunately, the implicit string to number conversion is not really documented in the MySQL manual. Most of the rules, however, can be deducted from the following part in Type Conversion in Expression Evaluation section of the manual:
For comparisons of a string column with a number, MySQL cannot use an
index on the column to look up the value quickly. If str_col is an
indexed string column, the index cannot be used when performing the
lookup in the following statement:
SELECT * FROM tbl_name WHERE str_col=1;1
The reason for this is that there are many different strings that may
convert to the value 1, such as '1', ' 1', or '1a'.
It is WHERE <condition>, e.g. WHERE col1 = 123. What you have instead is WHERE <number> or WHERE <string>, so there is an expression missing.
What would be possible though is WHERE <boolean>, and this is what MySQL expects. And as MySQL treats booleans like numbers (0 = false, other numbers = true), it looks for a number.
1 and 123 are numbers that result in true.
'2xyz' gets converted to 2, i.e. true.
'' and 'xyz' get converted to 0, i.e. false.
So the latter give you an empty result set as the where condition renders false.
In statement SELECT ... WHERE [where_condition], in where_condition expression you can use any of the functions and operators that MySQL supports, in which string literal is also supported. For strings the comparisons are based on the numeric values of the string unit. When evaluating an expression type conversion is also done.
So in above case the 2xyz gets converted to 2 which is true and hence you get all the records. Its like
SELECT * FROM tableName WHERE 2
and the string xyz gets converted to 0 which is false due to which you get empty result set. Its same as:
SELECT * FROM tableName WHERE 0
Where having condition value. Mysql any number treat as TRUE value and null or '' treat as FALSE.
1.SELECT * FROM tableName -- all record return
2.SELECT * FROM tableName WHERE 1 -- Return true value
3.SELECT * FROM tableName WHERE 123 -- Return true value
4.SELECT * FROM tableName WHERE '2xyz' -- Return true value because there first character is number
5.SELECT * FROM tableName WHERE '' -- false value return
6.SELECT * FROM tableName WHERE 'xyz' -- false value return
I have a sql query below:
SELECT
md.refereeInternetSearch,
md.refereeCompanyColleague,
md.refereeIndustryPeer,
md.refereeIndustryEvent,
md.refereeIndustryPublication,
md.refereeMarketingEmail,
md.refereeOther
FROM
marketing_details md
WHERE
md.id = 14588
From the 7 columns in the above select statement only one column will have a value and rest will be null. Is it possible to select just that one column value that is not null using some sort of sql statement ?
Use the coalesce() function to return the 1st non-null value from a list of parameters:
SELECT
coalesce(md.refereeInternetSearch,
md.refereeCompanyColleague,
md.refereeIndustryPeer,
md.refereeIndustryEvent,
md.refereeIndustryPublication,
md.refereeMarketingEmail,
md.refereeOther) as non_null_value
FROM
marketing_details md
WHERE
md.id = 14588
However, it will not be able to tell you which column the value came from.
UPDATE
If you really want to use sql to retrieve the name of the field that has the non null value, then you can do that with the following monstrous sql statement below. What it does it concatenates each field value from a record into a single string, where the values are separated by comma. NULL values are converted to empty string. Then using find_in_set() function it finds the position of the only non null value within the above string. Then using the elt() function it returns the name of the field from the list of field name literals based on the position returned by find_in_set().
SELECT
md.id,
coalesce(md.refereeInternetSearch,
md.refereeCompanyColleague,
md.refereeIndustryPeer,
md.refereeIndustryEvent,
md.refereeIndustryPublication,
md.refereeMarketingEmail,
md.refereeOther) as non_null_value,
elt(find_in_set(coalesce(md.refereeInternetSearch,
md.refereeCompanyColleague,
md.refereeIndustryPeer,
md.refereeIndustryEvent,
md.refereeIndustryPublication,
md.refereeMarketingEmail,
md.refereeOther),
concat(coalesce(md.refereeInternetSearch,''),',',
coalesce(md.refereeCompanyColleague,''),',',
coalesce(md.refereeIndustryPeer,''),',',
coalesce(md.refereeIndustryEvent,''),',',
coalesce(md.refereeIndustryPublication,''),',',
coalesce(md.refereeMarketingEmail,''),',',
coalesce(md.refereeOther,'')
)
),'refereeInternetSearch',
'refereeCompanyColleague',
'refereeIndustryPeer',
'refereeIndustryEvent',
'refereeIndustryPublication',
'refereeMarketingEmail',
'refereeOther'
) as field_name
FROM
marketing_details md
WHERE
md.id = 14588
Huh, I hope I got all the parentheses right!
According to MySQL Reference Manual - The SET Type
Normally, you search for SET values using the FIND_IN_SET() function or the LIKE operator:
mysql> SELECT * FROM tbl_name WHERE FIND_IN_SET('value',set_col)>0;
According to MySQL Reference Manual
FIND_IN_SET(str,strlist)
Returns a value in the range of 1 to N if the string str is in the string list strlist consisting of N substrings. A string list is a string composed of substrings separated by “,” characters. If the first argument is a constant string and the second is a column of type SET, the FIND_IN_SET() function is optimized to use bit arithmetic. Returns 0 if str is not in strlist or if strlist is the empty string. Returns NULL if either argument is NULL.
Therefore, I think that
SELECT * FROM tbl_name WHERE FIND_IN_SET('value',set_col)
works properly when you want to find value from a set.
So why does example from MySQL Reference Manual explicitly comparing with >0 ?
Is there any difference ?
Consider the following two WHERE clauses:
WHERE FIND_IN_SET('value', set_col) > 0
WHERE FIND_IN_SET('value', set_col)
In the first one, if any of the entries in sel_col contains value, then the return value for FIND_IN_SET() will be some number greater than 0, otherwise it will be 0. In other words, it will return TRUE if the value is found, and FALSE otherwise.
The second WHERE clause will evaluate to either WHERE X, where X is either 1 or greater, if value be found, or 0, if value be not found. In MySQL, the value 0 is synonymous with FALSE, and a positive number of 1 or greater is synonymous with TRUE (see documentation).
So these two WHERE clauses will behave identically.
I have a dataset which brings in distinct values of a column 'A' of table 'B' and these form the select values for a parameter 'Param_A'. In addition to this I have a main dataset which brings in data from table 'B' and contains the column 'A' as 'Field_A'.I do not want to alter the main dataset and hence I am using a tablix filter to filter out the result set of the main dataset. The tablix filter is supposed to be performing the below functionality :
Expression:
Fields!Field_A.value in (Parameter!Param_A.value) or Fields!Field_A.value is NUll
Boolean Operator :
"="
Value:
True
But I am unable to use the operator 'in'. It gives me an error.Could you please help me out with this?
I used the 'inStr' Operator which eliminated the possibility of using 'in' operator:
iif(InStr(Join(Parameters!Project.Value,","),Fields!project_name.value)>0,
true,false)
This helped me!
I have an SSRS report. It has a Marks dropdown, and a resultset "Classresult". When I select any value from Marks dropdown, it filters my result for selected value and displays the result.
Say when I select "100" from marks dropdown, it filters my Classresult dataset and shows all results with 100 value.
But it doesnot show values which have NULL in marks field.(the resultset ClassResult contains NULL values.
Is there any way i can include NULL values ??
Currently my condition is:
Marks == Parameters!Marks.Value
Do you have the ability to wrap an IsNull() around the Class result field in your datasource?
Like IsNull(ClassResult,0) AS Classresult
This will replace nulls with a zero. Alternately you could replace the 0 with a different value of your choice.
Use the IsNothing() function to check for a NULL value in an SSRS expression. It returns TRUE if the value is NULL.
You can include NULL in the query that populates the Marks drop down. (If you put the available values in statically, then add it there...) but here is how you can do it in the query.
SELECT ValueField, LabelField
FROM MarksTable
UNION
SELECT '(NULL)', '--NULL--'
Then in the query whose results you are filtering add
ISNULL([Marks], '(NULL)') as Marks