JPA concat operator

问题

Is there a JPA concat operator for string concatenation?

I know there is a JPA CONCAT function, however its ugly to use for concatenating multiple strings.

CONCAT(CONCAT(CONCAT(cola,colb),colc),cold)

Vendors like Oracle offer || some other like Microsoft offer +. Is there a standard JPA concatenation operator so that I could create a query like

cola || colb || colc || cold

I tried + using openjpa with SQL Server, however it seems to be invalid JPQL. I couldn't find anything regarding such an operator in an oracle reference.

回答1:

The CONCAT function was extended in JPA 2.0 to allow passing more than 2 parameters, from section 4.6.17.2.1 (String Functions) of the specification:

CONCAT(string_primary, string_primary {, string_primary}* )

In JPA 1 this was restricted to exactly two parameters.

回答2:

You can use JPA Concat function for multiple strings.

For example:

CONCAT(cola, colb, colc, cold)

回答3:

You can also use || as a concatenate operator, see on the documentation

HQL defines a concatenation operator in addition to supporting the concatenation (CONCAT) function. This is not defined by JPQL, so portable applications should avoid it use. The concatenation operator is taken from the SQL concatenation operator - ||.

Example 11.19. Concatenation operation example

select 'Mr. ' || c.name.first || ' ' || c.name.last
from Customer c
where c.gender = Gender.MALE

来源：https://stackoverflow.com/questions/8504457/jpa-concat-operator