Can't find ORA-00907: missing the right parenthesis - sql

Question

I don't know what is wrong with this syntax.
SELECT Count (id_conv) AS NUM_CAMP
FROM csd_mx_mae_camp_dro
WHERE id_conv = (SELECT id_conv
FROM csd_mx_mae_conv_dro
WHERE num_cta = 60385300500)
AND id_cncpt = (SELECT A.id_cncpt
FROM csd_mx_mae_camp_dro A
INNER JOIN csd_mx_mae_cncpt_dro B
ON A.id_cncpt = B.id_cncpt
WHERE ( ( flg_tipo_camp = 'A'
AND txt_nombr_clase_logic IS NOT NULL )
OR ( flg_tipo_camp = 'C' ) )
AND txt_nom NOT IN ( 'Concepto' )
AND B.txt_cve = '84'
AND A.id_conv = (SELECT id_conv
FROM csd_mx_mae_conv_dro
WHERE num_cta = 60385300500)
AND rownum = 1
ORDER BY id_cmp)
AND flg_tipo_camp = 'A';
The expected result is 4, taking into account my records in the DB, however I have the error mentioned in the title (ORA-00907: missing the right parenthesis
00907. 00000 - "missing right parenthesis"
* Cause:
* Action:
Error in the line: 171, column: 90).

Answer 1

There are some subqueries where ORDER BY makes sense - and it is allowed by the syntax.
However, you use ORDER BY in a scalar subquery - one that is required to return a single value (one row / one column), and such subqueries do not allow ORDER BY.
You are using it incorrectly anyway (most likely) - you limit the number of rows to 1 by the condition ROWNUM = 1, which in conjunction with your ORDER BY probably means you wanted to order by ID_CMP and then take the first row from the result. That is not how it works; ORDER BY comes only after ROWNUM is assigned anyway. If that's what you were trying to do, remove ORDER BY as well as the condition on ROWNUM, and instead select MIN(ID_CMP) in the SELECT clause of the scalar subquery.
The specific error about the missing right parenthesis is caused by the ORDER BY clause: at that point, in a scalar subquery, the parser expects the closing parenthesis for the subquery, not any other token/clause/whatever.