SQLite

      ** database table or a subquery.
      */
      Table *pTab = 0;            /* Table structure column is extracted from */
      Select *pS = 0;             /* Select the column is extracted from */
      int iCol = pExpr->iColumn;  /* Index of column in pTab */
      testcase( pExpr->op==TK_AGG_COLUMN );
      testcase( pExpr->op==TK_COLUMN );
      while( pNC && !pTab ){
        SrcList *pTabList = pNC->pSrcList;
        for(j=0;j<pTabList->nSrc && pTabList->a[j].iCursor!=pExpr->iTable;j++);
        if( j<pTabList->nSrc ){
          pTab = pTabList->a[j].pTab;
          pS = pTabList->a[j].pSelect;
        }else{
          pNC = pNC->pNext;
        }
      }

      if( pTab==0 ){
        /* At one time, code such as "SELECT new.x" within a trigger would
        ** cause this condition to run.  Since then, we have restructured how
        ** trigger code is generated and so this condition is no longer 
        ** possible. However, it can still be true for statements like
        ** the following:
        **
        **   CREATE TABLE t1(col INTEGER);
        **   SELECT (SELECT t1.col) FROM FROM t1;
        **
        ** when columnType() is called on the expression "t1.col" in the 
        ** sub-select. In this case, set the column type to NULL, even
        ** though it should really be "INTEGER".
        **
        ** This is not a problem, as the column type of "t1.col" is never
        ** used. When columnType() is called on the expression 
        ** "(SELECT t1.col)", the correct type is returned (see the TK_SELECT
        ** branch below.  */
        break;
      }

      assert( pTab && pExpr->pTab==pTab );
      if( pS ){
        /* The "table" is actually a sub-select or a view in the FROM clause
        ** of the SELECT statement. Return the declaration type and origin
        ** data for the result-set column of the sub-select.
        */
        if( ALWAYS(iCol>=0 && iCol<pS->pEList->nExpr) ){
          /* If iCol is less than zero, then the expression requests the
          ** rowid of the sub-select or view. This expression is legal (see 
          ** test case misc2.2.2) - it always evaluates to NULL.
          */
          NameContext sNC;
          Expr *p = pS->pEList->a[iCol].pExpr;
          sNC.pSrcList = pS->pSrc;
          sNC.pNext = pNC;
          sNC.pParse = pNC->pParse;
          zType = columnType(&sNC, p, &zOriginDb, &zOriginTab, &zOriginCol); 
        }
      }else if( ALWAYS(pTab->pSchema) ){
        /* A real table */
        assert( !pS );
        if( iCol<0 ) iCol = pTab->iPKey;

  } {one}
  do_test capi3c-23.6 {
    sqlite3_column_text16 $STMT 2
    sqlite3_column_text $STMT 3
  } {one}
  sqlite3_finalize $STMT
}

# Test decltype on some SELECT statements that contain sub-selects.
#
proc decltype {zSql} {
  set ret [list]
  set STMT [sqlite3_prepare_v2 db $zSql -1 TAIL]
  for {set i 0} {$i < [sqlite3_column_count $STMT]} {incr i} {
    lappend ret [sqlite3_column_decltype $STMT $i]
  }
  sqlite3_finalize $STMT
  return $ret
}
do_test capi3c-24.1 {
  execsql { CREATE TABLE t5(a INTEGER, b STRING, c DATETIME) }
  decltype {SELECT * FROM t5}
} {INTEGER STRING DATETIME}
do_test capi3c-24.2 {
  decltype {SELECT (SELECT c) FROM t5}
} {DATETIME}
do_test capi3c-24.3 {
  decltype {SELECT (SELECT * FROM (SELECT c)) FROM t5}
} {DATETIME}
do_test capi3c-24.4 {
  decltype {SELECT * FROM (SELECT * FROM t5 ORDER BY c LIMIT 1) ORDER BY b}
} {INTEGER STRING DATETIME}
do_test capi3c-24.5 {
  decltype {
    SELECT (SELECT x FROM (SELECT c AS x)) 
    FROM (SELECT * FROM t5 ORDER BY c LIMIT 1) ORDER BY b
  }
} {DATETIME}
do_test capi3c-24.3 {
  decltype {SELECT (SELECT x FROM (SELECT t5.a AS x)) FROM t5}
} {INTEGER}

finish_test