Placeholder while retrieving data from table - sql

Question

I have a table that contains common subjects text, that requires insertion of some string at run time. For example below:
CREATE TABLE certification.cert_email_dtls (
cert_eid_id numeric(10,0),
cert_eid_email_body character varying(8000),
);
insert into certification.cert_email_dtls(1,'hello world <blank-value1>);
insert into certification.cert_email_dtls(2,'hello guys <blank-other-value2>);
insert into certification.cert_email_dtls(3,'hello <blank-value3> india <some-other-value4>);
and so on. <some-value>,<some-other-value> etc come at run time.
SELECT cert_eid_id ,
cert_eid_email_body,
INTO v_id,
v_email_body_end
FROM certification.cert_email_dtls where cert_eid_id = in_id;
My requirement is to insert that some-values that are coming in between and generate the final email body.

Answer 1

format() might be the perfect tool for this. Read details in the manual.
If you can save cert_eid_email_body in a compatible format, like:
CREATE TABLE cert_email_dtls (
cert_eid_id serial PRIMARY KEY
, cert_eid_email_body text
);
INSERT INTO cert_email_dtls (cert_eid_email_body)
VALUES ('hello %1$s india %2$s');
The whole operation can be as simple as:
SELECT format(cert_eid_email_body, 'foo', 'bar', 'baz') AS cert_eid_email_body
FROM cert_email_dtls
WHERE cert_eid_id = 1;
Result:
cert_eid_email_body
-------------------
hello foo india bar
Note that the 3rd parameter 'baz' is silently ignored, since it is not referenced in the string.
SQL Fiddle.
Aside: Don't use numeric(10,0) for an ID or primary key. integer or bigint typically serve you better. Using serial PRIMARY KEY above as it probably should be.