Re: How concat 3 strings if 2 are not empty?

In response to Andreas :
> Hi,
>
> I'd like a function that concats 3 string parameters on condition the
> 1st and 3rd are NOT empty or NULL.
> xCat (s1, s2, s3)
> s2 would be a connector that appears only if s1 and s3 are set.
>
> NULL and an empty string '' should be handled the same.
>
> e.g.
> 'PostgreSQL', ' is ', ' great' --> 'PostgreSQL is great'
> NULL, ' is ', ' great' --> 'great'
> 'PostgreSQL', ' is ', NULL --> 'PostgreSQL'
> NULL, ' is ', NULL --> NULL
> 'PostgreSQL', NULL, ' great' --> 'PostgreSQL great'

Something like that?

test=*# select a,b,c, length(a), length(b), length(c) from string ;
a | b | c | length | length | length
------------+----+-------+--------+--------+--------
PostgreSQL | is | great | 10 | 2 | 5
PostgreSQL | is | | 10 | 2 |
PostgreSQL | | | 10 | |
| is | | | 2 |
| is | | 0 | 2 |
| is | | 0 | 2 | 0
(6 rows)

test=*#
test=*# select case when (a is null and c is null) or (a = '' and c = '') then null else coalesce(a,'') || coalesce(b,'')||coalesce(c,'') end from string;
case
-------------------
PostgreSQLisgreat
PostgreSQLis
PostgreSQL

is

(6 rows)

Andreas
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Andreas Kretschmer
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