How to check in hive whether the column is holding string character. My column is string datatype and has values like below
my_col string
000001234
0001111
One way to check, whether string character is present is following:
SELECT
my_col,
CASE WHEN HEX(LOWER(my_col)) <> HEX(UPPER(my_col)) then 'char present' else 'no char' END char_check
FROM my_table;
We convert value to lower case and upper case and cast it to hexadecimal.
HEX('1a') produces 3161
HEX('1A') produces 3141
And that's how we know that a character is present which can be converted to upper or lower case.
It's a quick workaround, otherwise I would create UDF with Java.
Related
I'm using SQL Server 2019.
select convert(bigint, ' ')
returns 0
select convert(numeric, ' ')
returns:
Error converting data type varchar to numeric.
Can anyone tell me why the behaviour between these two datatypes is different? I would have expected, that the second example returns 0 or 0.00.
From CAST and CONVERT:
"SQL Server also returns an error when an empty string (" ") is converted to numeric or decimal."
It's the documented behavior, that's why.
It's just the way it is implemented. Casting an empty string or a string with only spaces to an INT data type will result in 0. Some people regard this as logical behavior, others don't.
For a DECIMAL type, the same cast fails.
However, this is only true for spaces! Trying to cast other whitespace characters like tabs, carriage return or linefeed characters to an INT type will also fail.
If you want failed casts to return NULL instead of producing an error, you can use TRY_CONVERT instead:
select try_convert(numeric, ' ')
If you want both to behave in the same way (whether that would mean both returning NULL or both returning 0 or 0.0 respectively) you need to somehow work your way around it.
To have the cast to INT return NULL, you could e.g. combine TRY_CONVERT with NULLIF:
select try_convert(bigint, nullif(' ', ''))
This will also produce NULL for strings containing only (any number of) spaces.
If on the other hand, you prefer to see 0.0 results for empty strings or strings containing only spaces when casting to NUMERIC, you can filter these out explicitly:
select case when val like ' ' or val = '' then 0.0
else try_convert(numeric(5,1), val)
end as val
from strings
This db<>fiddle shows what results the different queries yield for various whitespace and non-whitespace string input.
Duration column in the table is given with 'varchar' data type. It contains decimal values. So I am trying to cast varchar to float/numeric/decimal/double/double precision. But none of those works. why is it not working?
select runner_id,
sum(case when cast(duration as decimal) <> '' then 1
else 0 end) as delivered, count(order_id) as total_orders
from t_runner_orders
group by runner_id
The reason it's not working is because your duration column contains values which cannot be cast to a numeric type. The specific value throwing the error is an empty string. Also, you shouldn't be comparing a numeric type to an empty string.
Also, if you're comparing a varchar column to a character value in your CASE statement, why are you trying to cast it to a numeric type at all?
For what you're doing here, I would just write it as CASE WHEN duration <> '' THEN 1 ELSE 0 END
And if you do need to cast it to a numeric type at some point, the way to do that would be something like CASE WHEN duration = '' THEN NULL ELSE cast(duration AS DECIMAL) END (asuming that empty strings are the only values in your column which cannot be cast to decimal)
The problem is you are doing the CAST before the <> ''. The cast fails as there are empty strings in the field. You have several choices:
Use NULL instead of '' in field.
Do duration <> ''
Last and probably the best long term solution change the column type to numeric.
You can translate '' to null using NULLIF in the cast.
cast(nullif(duration,'') as decimal) is not null
However this will not solve you basic problem which is "varchar' data type. It contains decimal values" NO it does not it contains a string which you hope are decimal values, but nothing prohibits putting 'zero.zero' into it - distinctly not a decimal value. I will go #AdrianKlaver one step further.
3. The only long term solution change the column type to numeric.
CASE
WHEN code IN ('FJS354', 'JDF334')
THEN 'Lower_form'
ELSE 0
END AS format
This returns an error in Redshift
invalid input syntax for integer: "Lower_form"
I know if I change 'Lower_form' to an integer it will work however I want this column to be a string. Is there a way to do this?
I want this column to be a string.
All branches of a case expression must return the same datatype. You are giving two literal values whose datatype is not the same (string vs integer): the database makes the decision to turn them both to integers - which is not what you want.
Rremove the ambiguity by being explicit about the datatype you want to return. That is, make this literal 0 a string:
CASE WHEN code in ('FJS354','JDF334')
THEN 'Lower_form'
ELSE '0'
END as format
I am new to SQL and I am looking at established queries that we have, can anyone explain what this statement means in the WHERE clause
(isnull(cast(field_name as CHAR), '') = '').
Breaking down each statement:
CAST(field_name AS CHAR) converts the field_name column to a CHAR
This value is then passed as the first argument to the ISNULL() with the second being an empty string ''.
ISNULL(CAST(field_name AS CHAR), '')
This takes the result of the cast, and if it's a NULL value, returns '' instead.
Finally, it checks if that result is equal to ''.
Essentially, it's checking for NULL or empty string values in one fell swoop.
juergen d is correct. I'd add that it tries to cast the field to alphanumeric before it checks if it is null or blank. If the field's data type has no defined conversion to type CHAR, the query will error out. Have a look at this regarding conversions/casts.
T-SQL Data Types and Conversion Info
I am trying to generate a hive query which will take multiple numeric column names and check whether it is has numeric values. If the column has numeric values then the output should be (column name,true) else if the field has NULL or some string value the output should be (column name,false)
SELECT distinct (test_nr1,test_nr2) FROM test.abc WHERE (test_nr1,test_nr2) not like '%[^0-9]%';
SELECT distinct test_nr1,test_nr2 from test.abc limit 2;
test_nr1 test_nr2
NULL 81432269
NULL 88868060
the desired output should be :
test_nr1 false
test_nr2 true
Since test_nr1 is a decimal field and it has NULL values, it should output false.
Appreciate valuable suggestions.
You can use cast function. It returns NULL when the value can not not be cast to numeric.
For example:
select case when cast('23ccc' as double) is null then false else true end as IsNumber;
You're trying to use character class pattern matching syntax here, and it doesn't work in every SQL implementation IIRC, however, regexp matching works in most, if not all, SQL implementations.
Considering you're using hive, this should do it:
SELECT ('test_nr1', test_nr1 RLIKE '\d'), ('test_nr2', test_nr2 RLIKE '\d') FROM test.abc;
You should remember that regexp matching is very slow in SQL though.