java - 如何使用空日期进行 SQL 查询？

Question

我想做这个查询:

    Class.forName("org.postgresql.Driver");
    Connection conn= null;
    conn = DriverManager.getConnection("jdbc:postgresql://localhost:5432/postgis","postgres","123456");
    PreparedStatement ps = null;
    String sql = "SELECT num FROM parcels WHERE code_initial_right =(SELECT code_document FROM documents WHERE number_document=? or date_document='"+docd+"')";
    ps = conn.prepareStatement(sql);
    ps.setString(1,docn);
    ResultSet rs = ps.executeQuery();

但是docd可以等于null。当我尝试这个时，我得到一个错误:

javax.servlet.ServletException: org.postgresql.util.PSQLException: ERROR: invalid input syntax for type date: ""

我能用它做什么？

Answer 1

使用 IS NULL 谓词:

....
OR docd IS NULL OR date_document = docd;