title: Extracting the month and year from a Timestamp on a Unique check?
body: <p>I'm trying to create a table with a timestamp column. The problem is, I want the month and the year combination to be unique. I tried this, but it doesn't help:</p>
  
  <pre><code>CREATE TABLE adempiere.SOIP_Deudas (
      --Columnas del sistema
      SOIP_Deudas_ID      numeric(10)     NOT NULL PRIMARY KEY,
      ad_client_id    numeric(10)     NOT NULL,
      ad_org_id   numeric(10)     NOT NULL,
      updatedby   numeric(10)     NOT NULL,
      createdby   numeric(10)     NOT NULL,
      updated     timestamp       NOT NULL,
      created     timestamp       NOT NULL,
      isactive    char(1)     DEFAULT 'Y'::bpchar NOT NULL,
  
      --Columnas del usuario
      SOIP_Departamentos_ID numeric(10) NOT NULL,
      fecha       timestamp   NOT NULL,
      monto       real        NOT NULL DEFAULT 0,
  
      FOREIGN KEY (SOIP_Departamatos_ID) REFERENCES SOIP_Departamentos(SOIP_Departamentos_ID),
      UNIQUE (EXTRACT (MONTH FROM TIMESTAMP fecha), EXTRACT(YEAR FROM TIMESTAMP fecha))
  )
  </code></pre>
  
  <p>Any idea of how I could do that without having specific Year and Month columns?</p>
  
  <p>Thanks.</p>