Does the JDBC spec prevent '?' from being used as an operator (outside of quotes)?

Question

From Sam Macbeth\'s question:

Is there anything in the JDBC spec which allows a ? to be escaped and be anything other than a parameter placeholder?

Answer 1

I don't see anything in the JDBC specification that would allow ? to be escaped. Pretty much all it says about ? is:

Parameter markers, represented by “?” in the SQL string, are used to specify input values to the statement that may vary at runtime. ^[1]

and later...

Parameter ordinals, which are integers passed to the approriate setter method, refer to the parameter markers ("?") in the statement, starting at one. ^[2]

And it only defines escape syntax for a small set of features, none of which look like they could be applied to ?:

JDBC defines escape syntax for the following:

• scalar functions
• date and time literals
• outer joins
• calling stored procedures
• escape characters for LIKE clauses ^[3]

Overall, it doesn't seem like the JDBC specification has very "strict" language (compared to, for example, some W3C specification documents which use must and should a lot), so I don't know whether a driver which allowed ? to be escaped would be technically non-compliant, but it would probably be not-so-compatible.

It doesn't even look like even the Postgres driver would allow it, as the method in the driver which actually parses SQL statements for ? doesn't check for any escape characters.

---

<sup>1. JDBC 4.1 Specification, Section 13.2 — The PreparedStatement Interface
2. JDBC 4.1 Specification, Section 13.3.2 — Setting Parameters
3. JDBC 4.1 Specification, Section 13.4 — Escape Syntax</sup>