Why I cannot call a function from within an SQL function?

Hi Ho!

The following query works well:

select count (*)
from item_audit
where audit_ts >= '2008-05-30 00:00:00'
and audit_ts <= '2008-10-30 00:00:00'
and 'wst' != (select split_part(category, '-', 2)
from description
where split_part(category, '-', 1) = 'item'
and shorthand = status
)

But, when I transform it into the following SQL function, the function cannot be created barking:

ERROR: syntax error at or near "-"
LINE 6: and $1 != (select split_part(category, '-', 2)"

create or replace function get_I(text, timestamp, timestamp) returns bigint as
'select count (*)
from item_audit as ia
where audit_ts >= $2
and audit_ts <= $3
and $1 != (select split_part(category, '-', 2)
from description
where split_part(category, '-', 1) = 'item'
and shorthand = ia.status
)
' language sql;

What's wrong?

Thank you.

Best regards,
Eus (FSF member #4445)

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