ERROR: invalid input syntax for type timestamp with time zone - postgresql

Question

I have a PostgreSQL query as below which is running fine . I am calling it from a shell script as below
Result=$(psql -U username -d database -t -c
$'SELECT round(sum(i.total), 2) AS "ROUND(sum(i.total), 2)"
FROM invoice i
WHERE i.create_datetime = '2019-03-01 00:00:00-06'
AND i.is_review = '1' AND i.user_id != 60;')
now I want the value which I have hard coded as i.create_datetime = '2019-03-01 00:00:00-06' to replace it with a variable date value.
I have tried two ways
way 1:
Result=$(psql -U username -d database -t -c
$'WITH var(reviewMonth) as (values(\'$reviewMonth\'))
SELECT round(sum(i.total),2) AS "ROUND(sum(i.total),2)"
FROM var,invoice i
WHERE i.create_datetime = var.reviewMonth::timestamp
AND i.is_review = \'1\' AND i.user_id != 60;')
and
way 2:
Result=$(psql -U username -d database -t -c
$'SELECT round(sum(i.total),2) AS "ROUND(sum(i.total),2)"
FROM invoice i
WHERE i.create_datetime = \'$reviewMonth\'
AND i.is_review = \'1\' AND i.user_id != 60;')
But both way it's throwing error
way 1 throwing error as :
ERROR: operator does not exist: timestamp with time zone = text
way 2 throwing error as :
ERROR: invalid input syntax for type timestamp with time zone: "$reviewMonth"
Please suggest what should be my approach.

Answer 1

You should try using the psql variables. Here's an example:
# Put the query in a file, with the variable TSTAMP:
> echo "SELECT :'TSTAMP'::timestamp with time zone;" > query.sql
> export TSTAMP='2019-03-01 00:00:00-06'
> RESULT=$(psql -U postgres -t --variable=TSTAMP="$TSTAMP" -f query.sql )
> echo $RESULT
2019-03-01 06:00:00+00
Note how we format the string literal substitution in the query: :'TSTAMP'
You could also do the substitution yourself. Here's an example using a heredoc:
> export TSTAMP='2019-03-01 00:00:01-06'
> RESULT=$(psql -U postgres -t << EOF
SELECT '$TSTAMP'::timestamp with time zone;
EOF
)
> echo $RESULT
2019-03-01 06:00:01+00
In this case, we aren't using psql's variable substitution, so we have to quote the variable like '$TSTAMP' . Using a heredoc makes the quoting much simpler than using -c because you aren't trying to quote the whole command.
EDIT: more examples because it appears this wasn't clear enough. TSTAMP does not have to be hard coded, it's just a bash variable than can be set like any other bash variable.
> TSTAMP=$(date -d 'now' +'%Y-%m-01 00:00:00')
> RESULT=$(psql -U postgres -t << EOF
SELECT '$TSTAMP'::timestamp with time zone;
EOF
)
> echo $RESULT
2019-06-01 00:00:00+00
However, if you're really just looking for the start of the month, there's no need for shell variables at all
> RESULT=$(psql -U postgres -t << EOF
SELECT date_trunc('month', now());
EOF
)
> echo $RESULT
2019-06-01 00:00:00+00