Category "coalesce"

Why do MySQL 8 IF and IFNULL return a BLOB result when testing a variable with value NULL?

Note: I have moved the essence of this question to here having learned some of what is happening but still wanting to understand. (In essence, ISNULL and COALES

Arel - How to coalesce a field and a string literal in an Arel query?

I inherited a big, complicated Arel query that pulled from a number of tables. A new requirement says that if one of those tabels doesn't have a value for a par

How to concatenate columns in a Postgres SELECT?

I have two string columns a and b in a table foo. select a, b from foo returns values a and b. However, concatenation of a and b does not work. I tried : sel

combine rows in data frame containing NA to make complete row

I know this is a duplicate Q but I can't seem to find the post again Using the following data df <- data.frame(A=c(1,1,2,2),B=c(NA,2,NA,4),C=c(3,NA,NA,5),D