SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.445 2008/07/01 18:26:50 danielk1977 Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.

**        (See ticket #2339)
**
**  (16)  The outer query is not an aggregate or the subquery does
**        not contain ORDER BY.  (Ticket #2942)  This used to not matter
**        until we introduced the group_concat() function.  
**
**  (17)  The sub-query is not a compound select, or it is a UNION ALL 

**        compound clause made up entirely of non-aggregate queries, and 
**        the parent query:
**
**          * is not itself part of a compound select,
**          * is not an aggregate or DISTINCT query, and
**          * has no other tables or sub-selects in the FROM clause.
**
**        The parent and sub-query may contain WHERE clauses. Subject to
**        rules (11), (13) and (14), they may also contain ORDER BY,
**        LIMIT and OFFSET clauses.
**
** In this routine, the "p" parameter is a pointer to the outer query.
** The subquery is p->pSrc->a[iFrom].  isAgg is true if the outer query
** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
**
** If flattening is not attempted, this routine is a no-op and returns 0.
** If flattening is attempted this routine returns 1.

  /* 
  ** Do not even attempt to generate any code if we have already seen
  ** errors before this routine starts.
  */
  if( pParse->nErr>0 ) goto select_end;










  /* ORDER BY is ignored for some destinations.
  */
  if( IgnorableOrderby(pDest) ){
    pOrderBy = 0;
  }

  /* Begin generating code.

        sqlite3ErrorMsg(pParse, "too many terms in compound SELECT");
        return 1;
      }
    }
    return multiSelect(pParse, p, pDest, aff);
  }
#endif

  /* If writing to memory or generating a set
  ** only a single column may be output.
  */
#ifndef SQLITE_OMIT_SUBQUERY
  if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){
    goto select_end;
  }
#endif

  /* If possible, rewrite the query to use GROUP BY instead of DISTINCT.
  ** GROUP BY may use an index, DISTINCT never does.
  */
  if( p->isDistinct && !p->isAgg && !p->pGroupBy ){
    p->pGroupBy = sqlite3ExprListDup(db, p->pEList);
    pGroupBy = p->pGroupBy;

# 2008 June 24
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library. 
#
# $Id: selectB.test,v 1.5 2008/07/01 18:26:51 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

proc test_transform {testname sql1 sql2 results} {
  set ::vdbe1 [list]
  set ::vdbe2 [list]

      SELECT a FROM t1 UNION ALL SELECT d FROM t2 UNION ALL SELECT c FROM t1
    ) WHERE a>=10 ORDER BY 1 LIMIT 3
  } {
    SELECT a FROM t1 WHERE a>=10 UNION ALL SELECT d FROM t2 WHERE d>=10
    UNION ALL SELECT c FROM t1 WHERE c>=10
    ORDER BY 1 LIMIT 3
  } {12 12 14}

  test_transform selectB-$ii.12 {
    SELECT * FROM (SELECT a FROM t1 UNION ALL SELECT d FROM t2 LIMIT 2)
  } {
    SELECT a FROM t1 UNION ALL SELECT d FROM t2 LIMIT 2
  } {2 8}

  test_transform selectB-$ii.13 {
    SELECT * FROM (SELECT a FROM t1 UNION ALL SELECT d FROM t2 ORDER BY a ASC)
  } {
    SELECT a FROM t1 UNION ALL SELECT d FROM t2 ORDER BY 1 ASC
  } {2 3 8 12 14 21}

  test_transform selectB-$ii.14 {
    SELECT * FROM (SELECT a FROM t1 UNION ALL SELECT d FROM t2 ORDER BY a DESC)
  } {
    SELECT a FROM t1 UNION ALL SELECT d FROM t2 ORDER BY 1 DESC
  } {21 14 12 8 3 2}

  test_transform selectB-$ii.14 {
    SELECT * FROM (
      SELECT a FROM t1 UNION ALL SELECT d FROM t2 ORDER BY a DESC
    ) LIMIT 2 OFFSET 2
  } {
    SELECT a FROM t1 UNION ALL SELECT d FROM t2 ORDER BY 1 DESC LIMIT 2 OFFSET 2
  } {12 8}

  test_transform selectB-$ii.15 {
    SELECT * FROM (
      SELECT a, b FROM t1 UNION ALL SELECT d, e FROM t2 ORDER BY a ASC, e DESC
    )
  } {
    SELECT a, b FROM t1 UNION ALL SELECT d, e FROM t2 ORDER BY a ASC, e DESC
  } {2 4 3 6 8 10 12 15 14 16 21 24}
}

do_test selectB-3.0 {
  execsql {
    DROP INDEX i1;
    DROP INDEX i2;
  }

    execsql {
      SELECT * FROM (SELECT e FROM t2 UNION ALL SELECT f FROM t2)
      INTERSECT 
      SELECT * FROM (SELECT e FROM t2 UNION ALL SELECT f FROM t2)
      ORDER BY 1
    }
  } {6 9 15 18 24 27}

  do_test selectB-$ii.17 {
    execsql {
      SELECT * FROM (
        SELECT a FROM t1 UNION ALL SELECT d FROM t2 LIMIT 4
      ) LIMIT 2
    }
  } {2 8}

  do_test selectB-$ii.18 {
    execsql {
      SELECT * FROM (
        SELECT a FROM t1 UNION ALL SELECT d FROM t2 LIMIT 4 OFFSET 2
      ) LIMIT 2
    }
  } {14 3}

  do_test selectB-$ii.19 {
    execsql {
      SELECT * FROM (
        SELECT DISTINCT (a/10) FROM t1 UNION ALL SELECT DISTINCT(d%2) FROM t2
      )
    }
  } {0 1 0 1}

  do_test selectB-$ii.20 {
    execsql {
      SELECT DISTINCT * FROM (
        SELECT DISTINCT (a/10) FROM t1 UNION ALL SELECT DISTINCT(d%2) FROM t2
      )
    }
  } {0 1}
}

finish_test