In my DB, some of values of a column (called status) are null, and if they are null, I want to show a String "canceled".
Guess I need to do it on Attributes - common -if-null but then don't know how to specify it.
Can anyone help me?
There are multiple options, as you said, Attributes - common - if-null on the field containing the status should do that, you can specify a String by entering it in the Value box. If your string disappears after unfocusing, click the ... while the Value entry is selected, that will launch a Popup-entrybox.
Alternatively, you could put that logic into your query
select coalesce(status, 'Cancelled')
from table
COALESCE
Evaluates the arguments in order and returns the current value of the first expression that initially doesn't evaluate to NULL. For example, SELECT COALESCE(NULL, NULL, 'third_value', 'fourth_value'); returns the third value because the third value is the first value that isn't null.
Some databases might have similar functions with different names, with Oracle e.g. there's nvl()
Related
I have a drop down in form that allow users to select multiple value at the same time in R Shiny and saving the record in SQLite DB at the back end and data type is VARCHAR
dropDown:
But when i click on save button i am getting below error:
Error in : Expecting a single string value: [type=character; extent=2].
Any help would be appreciated! :)
The error tells you all you need to know. Your selectInput is returning a vector of characters. Your database is expecting a scalar character. So, either turn the value of the selectInput into a scalar (by concatenation or pasting) or modify your database so that it can accept multiple rows of data which correspond to your input. The choice is yours.
I can't tell you which is more appropriate because you've provided no context.
If i don't specify value of default in informatica,what will it consider for default then?
My basic question is
Do both statement work same
DECODE(abc,'XYZ','XZ','OYE','KYA')
DECODE(abc,'XYZ','XZ','OYE','KYA',abc)
Return Value of DECODE
1.First_result if the search finds a matching value.
2.Default value if the search does not find a matching value.
3.NULL if you omit the default argument and the search does not find a matching value.
4. Even if multiple conditions are met, the Data Integration Service returns the first matching result.
5.If the data contains multibyte characters and the DECODE expression compares string data, the return value depends on the code page and data movement mode of the Data Integration Service.
So, in your first statement - NULL will returned if there is no Match.
And in the second stament, it returns the column data if there is no Match
I'm working with SQLite in Flash.
I have this unique index:
CREATE UNIQUE INDEX songsIndex ON songs ( DiscID, Artist, Title )
I have a parametised recursive function set up to insert any new rows (single or multiple).
It works fine if I try to insert a row with the same DiscID, Artist and Title as an existing row - ie it ignores inserting the existing row, and tells me that 0 out of 1 records were updated - GOOD.
However, if, for example the DiscId is blank, but the artist and title are not, a new record is created when there is already one with a blank DiscId and the same artist and title - BAD.
I traced out the disc id prior to the insert, and Flash is telling me it's undefined. So I've coded it to set anything undefined to "" (an empty string) to make sure it's truly an empty string being inserted - but subsequent inserts still ignore the unique index and add a brand new row even though the same row exists.
What am I misunderstanding?
Thanks for your time and help.
SQLite allows NULLable fields to participate in UNIQUE indexes. If you have such an index, and if you add records such that two of the three columns have identical values and the other column is NULL in both records, SQLite will allow that, matching the behavior you're seeing.
Therefore the most likely explanation is that despite your effort to INSERT zero-length strings, you're actually still INSERTing NULLs.
Also, unless you've explicitly included OR IGNORE in your INSERT statements, the expected behavior of SQLite is to throw an error when you attempt to insert a duplicate INDEX value into a UNIQUE INDEX. Since you're not seeing that behavior, I'm guessing that Flash provides some kind of wrapper around SQLite that's hiding the true behavior from you (and could also be translating empty strings to NULL).
Larry's answer is great. To anyone having the same problem here's the SQLite docs citation explaining that in this case all NULLs are treated as different values:
For the purposes of unique indices, all NULL values are considered
different from all other NULL values and are thus unique. This is one
of the two possible interpretations of the SQL-92 standard (the
language in the standard is ambiguous). The interpretation used by
SQLite is the same and is the interpretation followed by PostgreSQL,
MySQL, Firebird, and Oracle. Informix and Microsoft SQL Server follow
the other interpretation of the standard, which is that all NULL
values are equal to one another.
See here: https://www.sqlite.org/lang_createindex.html
I am writing a code that calls a column from a dataset using a SQL query. I use two parameters to identify which rows to select. One is the ProductSerialNumber, and the other is a datetimestamp. See my SQL query below
Select TestStation FROM tblData
WHERE ProductSerialNumber = ? AND Datetimestamp = ?
In the dataset's datatable the productserialnumber is formatted as text, and the other is formatted as a date (as you would expect).
In my vb.net code, I grab the Datetimestamp from another source (don't ask why, the only thing you need to know is that it grabs a valid datetimestamp, dimensioned as a date, that matches exactly with the tblData's entry) and I use the premade query to generate a datatable. The query is a Fill query called "TestStationLookUp"
my vb.net code looks like this
Dim dt as new dataset.tbldataDataTable
Dim dta As New DataSetTableAdapters.tbldataTableAdapter
Dim ProductSerialNumber as string = "XXXXXX"
Dim DateTimeStamp as date = SomeDateVariable
dta.TestStationLookUp(dt, ProductSerialNumber, DateTimeStamp)
It is here that the code tells me:
Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
Line 7366: dataTable.Clear
Line 7367: End If
Error: Line 7368: Dim returnValue As Integer = Me.Adapter.Fill(dataTable)
Line 7369: Return returnValue
Line 7370: End Function
I cannot understand why this error arises, as everything is dimensioned the way it should be. This exact code setup works elsewhere in my code (except it doesn't use a date), but this specific piece won't work.
Also, if I go to the dataset in my solution, I can use the "preview data" on this query and type in the EXACT same parameters (the ProductSerialNumber and DateTimeStamp that match the record in the table AND what I use in my vb code) and it will give me produce the table I want.
Can anyone assist?
This error means that you are trying to access not valid unique id "ProductSerialNumber", maybe it does not exist
Failed to enable constraints. One or more rows contain values
violating non-null, unique, or foreign-key constraints.
Instead of passing the variable that comes from dataset ,pass a valid number that you are sure it exists in database
Is there a documentation/specification about Sqlite3 that would describe would is supposed to happen in the following case?
Take this query:
var cmd = new SqliteCommand("SELECT Items.*, Files.* FROM Items LEFT JOIN Files ON Files.strColName = Items.strColName");
Both Items and Files have a column name "strColName". If an entry exists in Files, it will be joined to the result, if not, it will be NULL.
Let's assume I always need the value of strColName, no matter if it is coming from Items or from Files. If I execute a reader:
var reader = cmd.ExecuteReader();
If there is a match in Files, reader["strColName"] will obviously contain the correct result because the value is set and it is the same in both tables. But if there wasn't a match in Files, will the NULL value of Files overwrite the non-NULL value of Items?
I'm really looking for some specification that defines how a Sqlite3 implementation has to deal with this case, so that I can trust either result.
SQLite has no problem returning multiple columns labelled with the same name.
However, the columns will always be returned in exactly the same order they are written in the SELECT statement.
So, when you are searching for "strColName", you will find the first one, from Items.
It is recommended to use explicit column names instead of * so that the order is clear, and you can access values by their column index, if needed (and you detect incompatible changes in the table structure).