There seems to be inconsistencies with how ERROR-01722 error worked, for those who don't know the issue is due to an invalid number and to fix it you'll need to wrap the number to char.
But when filtering VARCHAR2 it is stated that Oracle will convert the data of the column being filtered based on the value given to it. (see: https://stackoverflow.com/a/10422418/5337433)
Now that this is explained for some reason, the error is inconsistent. As an example I have this query:
In this example filter1 is varchar2
select *
from table
where filter1 = 12345
and filter2 = ''
and filter3 = '';
When this statement run there were no issues, but when you run it like this:
select *
from table
where filter1 = 12345
and filter2 = '';
it errors out to ERROR-01722, im not sure why it is acting this way, and how to fix it.
When you compare a varchar column to a number, Oracle will try to convert the column's content to a number, not the other way round (because 123 could be stored as '0123' or '00123')
In general you should always use constant values that match the data type of the column you compare them with. So it should be:
where filter1 = '12345'
However if you are storing numbers in that column, you should not define it as varchar - it should be converted to a proper number column.
The reason the error doesn't show up "consistently" is that you seem to have some values that can be converted to a number and some can't. It depends on other conditions in the query if the those values are included or not.
Additionally: empty strings are converted to NULL in Oracle. So the condition filter2 = '' will never be true. You will have to use filter2 is null if you want to check for an "empty" column.
Related
I've written the following SQL query to return all sites having "id" equal to 2.
SELECT * FROM `sites` WHERE id = '2'
And it works well. The problem is that even if I add some characters after "2" like this :
SELECT * FROM `sites` WHERE id = '2etyupp-7852-trG78'
It returns the same results as above.
How to avoid this ? that's to say return none on the second query ?
Thanks
The reason is that you are mixing types:
where id = '2'
------^ number
-----------^ string
What is a SQL engine supposed to do? Well, the standard approach is to convert the string to a number. So this is run as:
where id = 2
What happens when the string is not a number? In most databases, you get a type conversion error. However, MySQL does implicit conversion, converting the leading digits to a number. Hence, your second string just comes 2.
From this, I hope you learn not to mix data types. Compare numbers to numbers. Compare strings to strings.
I have tables A and B that share several fields and have the same datatype/length and I'm trying to get additional information to B and for that I need to do a match on case_number.
The problem is case_number in table A has a length of 10 and anything less than 10 is preceded with zeros (i.e 84534 --> 0000084534) table B does not (84534 = 84534) So when I attempt to match on case_number I get no results. Both fields are varchar2 and this is Oracle and I'm unable to modify table A.
I tried to use LPAD and that does not seem to help. I need a function to work in select statement.
The simplest solution seems to be to left-pad the string from the second table with zeros:
...
where a.case_number = lpad(b.case_number, 10, '0')
...
Alternatively, you could leave b.case_number unchanged and left-trim '0' from a.case_number, but this will only work if you can guarantee that b.case_number never has leading zeros (and, in particular, that b.case_number can't be zero).
...
where ltrim(a.case_number, '0') = b.case_number
...
One method is to convert to a number:
to_number(x) = to_number(y)
This has been bothering me with my coding continuously and I can't seem to google a good workaround.
I have a number of columns which are data type nvarchar(255). Pretty standard I would assume.
Anyway, I want to run:
DELETE FROM Ranks WHERE ISNULL(INST,0) = 0
where INST is nvarchar(255). I am thrown the error:
Conversion failed when converting the nvarchar value 'Un' to data type int.
which is the first non null in the column. However, I don't care for this showing me the error means it's not null? - I just want to delete the nulls!
Is there something simple I'm missing.
Any help would be fab!
An expression may only be of one type.
Expression ISNULL(INST,0) involves two source types, nvarchar(255) and int. However, no type change happens at this point, because ISNULL is documented to return the type of its first argument (nvarchar), and will convert the second argument to that type if needed, so the entire original expression is equivalent to ISNULL(INST, '0').
Next step is the comparison expression, ISNULL(INST, '0') = 0. It again has nvarchar(255) and int as the source data types, but this time nothing can stop the conversion - in fact, it must happen for the comparison operator, =, to even work. According to the data type precedence list, the int wins, and is chosen as the resulting type of the comparison expression. Hence all values from column INST must be converted to int before the comparison = 0 is made.
If you
just want to delete the nulls
, then just delete the nulls:
DELETE FROM Ranks WHERE INST IS NULL
If for some reason you absolutely have to use isnull in this fashion, which there is no real reason for, then you should have stayed in the realm of strings:
DELETE FROM Ranks WHERE ISNULL(INST, '') = ''
That would have deleted null entries and entries with empty strings (''), just like the WHERE ISNULL(INST, 0) = 0 would have deleted null entries and entries with '0's if all values in INST could have been converted to int.
With ISNULL(INST,0) you are saying: If the string INST is null, replace it with the string 0. But 0 isn't a string, so this makes no sense.
With WHERE ISNULL(INST,0) = 0 you'd access all rows where INST is either NULL or 0 (but as mentioned a string is not an integer).
So what do you want to achieve? Delete all rows where INST is null? That would be
DELETE FROM ranks WHERE inst IS NULL;
I'm needing to return values in SQL query that are either null or 2 for broker reason codes. I've tried using a.BROKER_REASON in (2,null), but it only pulls back 2's. I've tried using "a.BROKER_REASON is null or a.BROKER_REASON = 2" and get error msg "Conversion failed when converting the varchar value '+MULTI' to data type int." Is there an easy way to return rows with null values or values of 2?
That error looks more like your value stored isn't an actual number but rather a small string.
Try:
a.BROKER_REASON is null or a.BROKER_REASON = '2'
If not you may have extra spaces there stored, and can happen depending on storage engines/table definitions, in which case you can do a LTRIM or LEFT (depends on what SQL database you use) or equivalent to trim off excess spaces.
I am trying to connect a Filemaker DB to Firebird SQL DB in both ways import to FM and export back to Firebird DB.
So far it works using the MBS Plug-in but FM 13 Pro canot handle NULL.
That means that for example Timestamp fields that are empty (NULL) produce a "0" value.
Thats means in Time something like 01.01.1889 00:00:00.
So my idea was to simply ignore fields containing NULL.
But here my poor knowlege stops.
First I thought I can do this with WHERE, but this is ignoring whole records sets:
SELECT * FROM TABLE WHERE FIELD IS NOT NULL
Also I tried to filter it later on like this:
If (IsEmpty (MBS("SQL.GetFieldAsDateTime"; $command; "FIELD") ) = 0 ; MBS("SQL.GetFieldAsDateTime"; $command; "FIELD"))
With no result either.
This is a direct answer to halfbit's suggestion, which is correct but not for this SQL dialect. In a query to provide a replacement value when a field is NULL you need to use COALESCE(x,y). Where if X is null, Y will be used, and if Y is null then the field is NULL. Thats why it is common for me to use it like COALESCE(table.field,'') such that a constant is always outputted if table.field happens to be NULL.
select COALESCE(null,'Hello') as stackoverflow from rdb$database
You can use COALESCE() for more than two arguments, I just used two for conciseness.
I dont know the special SQL dialect, but
SELECT field1, field2, value(field, 0), ...FROM TABLE
should help you:
value gives the first argument, ie, your field if it is NOT NULL or the second argument if it is.