Concatenación es unir dos variables tipo string (cadena de texto) en un solo conjunto....
expression || expression String concatenation (two vertical bars). If either string is the NULL value, it is treated as the empty string for concatenation.
expression + expression Alternative string concatenation. When using the + concatenation operator, you must ensure the operands are explicitly set to character data types rather than relying on implicit data conversion.
Standards and compatibility
· SQL/92 The || operator is the SQL/92 string concatenation operator.
· Sybase The + operator is supported by Adaptive Server Enterpris
ej... 'A' + 'B' al concatenar ... = 'AB'
a='AB'
b='BC'
a+b='ABBC'
Espero que te sirva.
