Using “NULL” as a character string  Connecting expressions

Chapter 4: Expressions, Identifiers, and Wildcard Characters

NULL compared to the empty string

The empty string (“ ”or ‘ ’) is always stored as a single space in variables and column data. This concatenation statement is equivalent to “abc def”, not to “abcdef”:

"abc" + "" + "def"

The empty string is never evaluated as NULL.





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