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Chapter 3 Supplement

Chapter 3 Supplement. Self-joins Using PROC SQL. Self-Joins. Self-joins, or Reflexive Joins are used to compare values within a data set Examples typically use equality operations to create a join. 2011 SEC Football Scores. Self-Joins.

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Chapter 3 Supplement

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  1. Chapter 3 Supplement Self-joins Using PROC SQL

  2. Self-Joins • Self-joins, or Reflexive Joins are used to compare values within a data set • Examples typically use equality operations to create a join

  3. 2011 SEC Football Scores

  4. Self-Joins • Note that USC’s winning score on November 12 matches Mississippi State’s losing score on November 19 • We can record all such instances using a reflexive join • The reflexive join can look like an outer union

  5. Self-Join Syntax proc sql; select winner.wscore, winner.date, winner.wteam, loser.date, loser.lteam from secscores as winner, secscores as loser where winner.wscore=loser.lscore; quit;

  6. Self-Join Syntax • We do not have to use equality operators: proc sql; select winner.wscore, winner.date, winner.wteam, loser.date, loser.lteam from secscores as winner, secscores as loser where winner.wscorelt loser.lscore; quit;

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