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Parameters and Rules

Empty String Parameters​

Positional parameters, named parameters, and JDBC PreparedStatement can bind strings, but Oracle treats an empty VARCHAR2 string as NULL. The binding method does not change this behavior: writing "" does not return the same empty string when read.

CREATE TABLE text_example (id NUMBER(10) PRIMARY KEY, note VARCHAR2(100));
jdbcTemplate.executeUpdate("INSERT INTO text_example (id, note) VALUES (?, ?)",
        new Object[] { 1, "" });
String note = jdbcTemplate.queryForObject(
        "SELECT note FROM text_example WHERE id = ?", new Object[] { 1 }, String.class);
// note is null

The same applies when a method annotation or Mapper file binds "" through #{note}. Use IS NULL to find these rows. If the application must distinguish an absent value from an empty string, store the distinction in a separate status field.

Parameter Reuse​

PreparedStatement supports rebinding and executing again, but reuse does not change empty-string storage semantics. Use the status field described above if the application must preserve the distinction between "" and null.

See Where Builder for querying empty strings and batching large ID collections.