Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
514 views
in Technique[技术] by (71.8m points)

.net - SQLite equivalent to ISNULL(), NVL(), IFNULL() or COALESCE()

I'd like to avoid having many checks like the following in my code:

myObj.someStringField = rdr.IsDBNull(someOrdinal) 
                            ? string.Empty 
                            : rdr.GetString(someOrdinal);

I figured I could just have my query take care of the nulls by doing something like this:

SELECT myField1, [isnull](myField1, '') 
FROM myTable1
WHERE myField1 = someCondition

I'm using SQLite though and it doesn't seem to recognize the isnull function. I've also tried some equivalent ones recognized in other databases (NVL(), IFNULL() and COALESCE()), but SQLite doesn't seem to recognize any of them.

Does anyone have any suggestions or know of a better way to do this. Unfortunately the database doesn't have default values for all fields. Plus, I need to use some LEFT JOIN clauses in some cases, where some of the fields returned will be null because the matching record in the LEFT JOIN table will not exist.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Answer

0 votes
by (71.8m points)

IFNULL, see here: http://www.sqlite.org/lang_corefunc.html#ifnull

no brackets around the function


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...