In SQL:
I want to check. From single table,
if(field1 = 1 and DATE_SUB(CURDATE(),INTERVAL 7 DAY) <= field2) then
return count(*)
else
return "false"
thanks
v.srinath
SELECT CASE WHEN (field1 = 1 AND DATE_SUB(CURDATE(),INTERVAL 7 DAY) <= field2)
THEN COUNT(*)
ELSE 0
END
FROM SomeTable
CASE
WHEN field1 = 1
AND DATE_SUB(CURDATE(),INTERVAL 7 DAY) <= field2
THEN COUNT(*)
ELSE 'false'
END
Note that this only works in the SELECT list, or HAVING clause, and you should have a GROUP BY clause on field1 and field2. The reason is that COUNT() is an aggregate function. Because field1 and field2 appear outside an aggregatee function, aggregation for those fields must be enforced with a GROUP BY clause. Most RDBMS-es won't allow you to write this unless there is an appropriate GROUP BY clause, but MySQL will, and will silently return rubbish for those fields.
BTW - I think you should probably not write "false" but simply FALSE - right now both legs of the choice have a different type (boolean vs string). The db will probably coerce types, but it is still bad practice. You should ensure that the expression for each brach of the CASE expression have the same data type.
Related
I have column which should only contain numbers[0-9], But in some cases we started see alphanumeric[eg:p8eSadfghrc] values in that column.
I wanna write a condition where if the value is not completely numeric{0-9}, i wanna replace it with another value from another column.
Something like this?
update t
set col = <other value>
where regexp_like(col, '[^0-9]');
This updates the data. You could also just do this in a query:
select t.*,
(case when regexp_like(col, '[^0-9]') then <other value> else col end)
from t;
In Snowflake, I would recommend try_to_decimal(). It attempts to convert the number to a decimal value (you control the target precision and scale with arguments) and rturns null if that fails:
select t.*, case when try_to_decimal(mycol) is null then myothercol else mycol end newcol
from mytable
If you want an update statement:
update mytable
set mycol = myothercol
where try_to_decimal(mycol) is null
When given no second and third argument, the number of allowed digits is 38, with 0 decimals (which seems to be what you want).
I have a code like that:
select
tbl.person
,COUNT(distinct tbl.project)
,if (tbl.stage like '%SIGNED%') then sum(tbl.value) else '0' end if as test
from
my_table tbl
group by
1
And it returns me that error message:
SQL Error [42601]: ERROR: syntax error at or near "then"
I didn't got it. As I saw on documentation, the if statement syntax appears to be used correctly
IF is to be used in procedures, not in queries. Use a case expression instead:
select
tbl.person
,COUNT(distinct tbl.project)
,sum(case when tbl.stage like '%SIGNED%' then tbl.value else 0 end) as test
from
my_table tbl
group by
1
Notes:
tbl.stage is not part of the group by, so it should most probably be enclosed within the aggregate expression, not outside of it
all values returned by a case expression need to have the same datatype. Since sum(tbl.value) is numeric, the else part of the case should return 0 (number), not '0' (string).
In Postgres, I would recommend using filter:
select tbl.person, COUNT(distinct tbl.project)
sum(tbl.value) filter (where tbl.stage like '%SIGNED%') as test
from my_table tbl
group by 1;
if is control flow logic. When working with queries, you want to learn how to think more as sets. So the idea is to filter the rows and add up the values after filtering.
replace
if (tbl.stage like '%SIGNED%') then sum(tbl.value) else '0' end if as test
with
sum(case when tbl.stage like '%SIGNED%' then tbl.value end) as test
I have a SQL query, linking table 1 to table 2 via an inner join, containing this part in the select part of the statement:
select
table1.field1,
table2.field1,
CASE (table2.field1)
WHEN -2 THEN ''
ELSE table2.field2
END as table2Field2,
table3.field4
from...
I want to be able to return table2Field2 when it has a relevant value, ie: when the object represented in table2 is not null, so that table2.field1 does not have a value of -2. In this case, the value of table2Field2 should be blank instead of a meaningless value.
However, this returns 0 instead of the blank text. If I change this line:
WHEN -2 THEN ''
to this:
WHEN -2 THEN 'someText'
then it complains at me that it's trying to convert an int to a string, which I'm not. table2field1 is an int, but table2Field2 is a string, which is what we're actually returning here.
How do I state (even more specifically) in this query that I'm returning the string field as a string, and not something else as a string that isn't (a) a string, and (b) the thing I specified I'm returning please?
All suggestions welcome, many thanks in advance for any help :)
In a CASE expression, all of the possible return values must be of the same data type. As written, the expression is trying to return one string and one integer.
If you want an empty string for your first output, you can CAST or CONVERT your second output to a character type value:
select
table1.field1,
table2.field1,
CASE (table2.field1)
WHEN -2 THEN ''
ELSE CAST(table2.field2 AS varchar(12)) --< 12 will cover any value of integer.
END as table2Field2,
table3.field4
from...
Is it possible you have your as table2field2 in the wrong location?
maybe try:
select
table1.field1,
table2.field1,
CASE (table2.field1)
WHEN -2 THEN ''
ELSE table2.field2
END as table2Field2,
table3.field4
from...
Because you do not want to answer me what is the database you use then I have to do it like this hehehe:
SQL Server: DEMO
select
t.col1,
CASE
WHEN convert(char,t.col1) = '-2' THEN 'aaa'
ELSE convert(char,(t.col2))
END test
from Tab1 t;
Oracle DEMO
select
t.col1,
CASE
WHEN to_char(t.col1) = '-2' THEN 'aaa'
ELSE to_char(t.col2)
END test
from tab1 t;
I have the following query:
select case when count(*)>0 then true else false end
from tab
where param in ('a','b') and position('T' in listofitem)>0
This checks if 'T' exists in the column listofitem and if it does the count is > 0. Basically it's a search for sub string.
This works well in this private case. However my real case is that I have text[] called sub_array meaning multiple values to check. How can I modify the query to handle the sub_array type? I prefer to have it in a query rather than a function with a LOOP.
What I actualy need is:
select case when count(*)>0 then true else false end
from tab
where param in ('a','b') and position(sub_array in listofitem)>0
This is not working since sub_array is of type Text[]
Use the unnest() function to expand your array & bool_and() (or bool_or() -- this depends on what you want match: all array elements, or at least one) to aggregate:
select count(*) > 0
from tab
where param in ('a','b')
and (select bool_and(position(u in listofitem) > 0)
from unnest(sub_array) u)
A brute force method would be to convert the array to a string:
select (count(*) > 0) as flag
from tab
where param in ('a','b') and
array_to_string(listofitem, '') like '%T%';
I should note that comparing count(*) is not the most efficient way of doing this. I would suggest instead:
select exists (select 1
from tab
where param in ('a','b') and
array_to_string(listofitem, '') like '%T%'
) as flag;
This stops the logic at the first match, rather than counting all matching rows.
Is there a way to have a query return either a 'Y' or 'N' for a column if that column has a value above a certain number say '25'.
I am using DB2 on ZOS
SELECT CASE WHEN Col1 > 25 THEN 'Y' ELSE 'N' END As Value1
FROM Table1
For MySQL:
SELECT IF(column > 25, 'Y', 'N')
FROM table
http://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html#function_if
There is a IF block for SQL.
http://sqltutorials.blogspot.com/2007/06/sql-ifelse-statement.html
Use the SQL CASE statement
SELECT CASE WHERE columnname > 25 THEN 'Y' ELSE 'N' END FROM table;
select
case when somecolumn > 25 then 'Y' else 'N' end as somename
from sometable;
Select If(myColumn > 25, 'Y', 'N') From myTable
Apart from the IF and CASE statements another valid alternative is to create a user defined function feeding in your column value and returning Y or N.
This has the not inconsiderable advantage that if you are selecting on this criteria in more than on SQL statement and at a later date your condition changes - to over 30 say - then you have only one place to change your code. Although using a function adds complexity and overhead so is not always optimal don't underestimate the maintenance advantage of this approach. A minor plus too is you can make the name of the function something more meaningful, and hence self documenting, than an inline CASE