我无法获得正确的语法 - 我正在尝试将列匹配为空字符串,而不是 null。我已经尝试使用单双引号以多种方式分隔字符串。
containerRefNo = "\"\"";
ps = getConnection().prepareStatement(
"delete from inumber_join where container_no = ?");
我收到的错误是
You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'from inumber_join where container_no = '""''
最佳答案
使用参数化查询时,您不需要在参数值中包含任何 分隔符。只需使用 ps.setString(1, "");
对我来说效果很好。
也就是说,...
// setup
try (Statement st = conn.createStatement()) {
st.executeUpdate(
"CREATE TEMPORARY TABLE inumber_join_temp (" +
"id INT AUTO_INCREMENT, " +
"container_no VARCHAR(10) NULL, " +
"PRIMARY KEY (id)" +
")");
st.executeUpdate(
"INSERT INTO inumber_join_temp (container_no) " +
"VALUES (null), (''), (null), (''), (null)");
}
// test
String sql =
"SELECT COUNT(*) AS n " +
"FROM inumber_join_temp " +
"WHERE container_no = ?";
try (PreparedStatement ps = conn.prepareStatement(sql)) {
ps.setString(1, ""); // search for empty string
try (ResultSet rs = ps.executeQuery()) {
rs.next();
System.out.println(rs.getInt(1));
}
}
...返回
2
关于mysql - 匹配 MySQL 列中的空字符串,而不是空值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/32891927/