title: Oracle 12c - Column check constraint cannot reference other column
body: <p>I have to modify my table and I try do it as following:</p>
  
  <pre><code>ALTER TABLE projects
      MODIFY (
          id_proj NUMBER(4) CONSTRAINT pk_proj PRIMARY KEY,
          desc VARCHAR2(40) NOT NULL CONSTRAINT uk_proj UNIQUE,
          end_date CONSTRAINT chk_date CHECK(end_date &gt; start_date),
          fund CHECK (fund &gt; 0)
      );
  </code></pre>
  
  <p>And when I try execute this query I get an error:</p>
  
  <blockquote>
    <p>ORA-02438: Column check constraint cannot reference other columns<br>
    02438. 00000 -  "Column check constraint cannot reference other columns"<br>
    *Cause:    attempted to define a column check constraint that references
               another column.<br>
    *Action:   define it as a table check constraint.</p>
  </blockquote>
  
  <p>Additionally I want the column to accept values greater than 0 or NULL values.</p>