MYSQL-opregning:@rownum, ulige og lige poster

De er tabelaliaser, så du behøver ikke at angive hele tabellens navn, når du skal lave reference.

For kun at få de ulige nummererede poster, brug:

SELECT x.*
  FROM (SELECT u.pg_id AS ID, 
               u.pg_url AS URL,
               u.pg_title AS Title,
               u.pg_content_1 AS Content,
               @rownum := @rownum + 1 AS rownum
          FROM root_pages u
          JOIN (SELECT @rownum := 0) r
         WHERE u.parent_id = '7'
           AND u.pg_id != '7'
           AND u.pg_cat_id = '2'
           AND u.pg_hide != '1'
      ORDER BY u.pg_created DESC) x
WHERE x.rownum % 2 != 0

For at få de lige nummererede poster, brug:

SELECT x.*
  FROM (SELECT u.pg_id AS ID, 
               u.pg_url AS URL,
               u.pg_title AS Title,
               u.pg_content_1 AS Content,
               @rownum := @rownum + 1 AS rownum
          FROM root_pages u
          JOIN (SELECT @rownum := 0) r
         WHERE u.parent_id = '7'
           AND u.pg_id != '7'
           AND u.pg_cat_id = '2'
           AND u.pg_hide != '1'
      ORDER BY u.pg_created DESC) x
WHERE x.rownum % 2 = 0

Forklaring

% er moduloperatoren i MySQL-syntaks -- den returnerer resten af ​​divisionen. For eksempel er 1 % 2 0,5, mens 2 % 2 er nul. Dette bruges derefter i WHERE-sætningen til at filtrere de viste rækker.