问题
I have a column which contains null values in some of the rows.
I want to do sum of the column values by writing a select statement in sqlite.
How do I write the statement so that it treats null values as 0.
My current sqlite statement: select sum(amount) from table1 gives error as it returns null.
Please help.
回答1:
You can use ifnull(x,y) or coalesce(x,y,z,...) function. Each of them return the first non-null value from the parameter list from left to right. ifnull has exactly two parameter whereas coalesce has at least two.
select sum(ifnull(amount, 0)) from table1
回答2:
Accordgin to SQLite documentation:
The sum() and total() aggregate functions return sum of all non-NULL values in the group. If there are no non-NULL input rows then sum() returns NULL but total() returns 0.0. NULL is not normally a helpful result for the sum of no rows but the
So I guess you'd better use total() instead of sum() in case you expect that the result be 'non-null'.
来源：https://stackoverflow.com/questions/4176517/how-to-write-sqlite-select-statement-for-null-records