SQLite-2.5.0-for-code-reading/test/subselect.test

# 2001 September 15
#
# 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.  The
# focus of this file is testing SELECT statements that are part of
# expressions.
#
# $Id: subselect.test,v 1.5 2002/05/26 20:54:35 drh Exp $

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

# Basic sanity checking.  Try a simple subselect.
#
do_test subselect-1.1 {
  execsql {
    CREATE TABLE t1(a int, b int);
    INSERT INTO t1 VALUES(1,2);
    INSERT INTO t1 VALUES(3,4);
    INSERT INTO t1 VALUES(5,6);
  }
  execsql {SELECT * FROM t1 WHERE a = (SELECT count(*) FROM t1)}
} {3 4}

# Try a select with more than one result column.
#
do_test subselect-1.2 {
  set v [catch {execsql {SELECT * FROM t1 WHERE a = (SELECT * FROM t1)}} msg]
  lappend v $msg
} {1 {only a single result allowed for a SELECT that is part of an expression}}

# A subselect without an aggregate.
#
do_test subselect-1.3a {
  execsql {SELECT b from t1 where a = (SELECT a FROM t1 WHERE b=2)}
} {2}
do_test subselect-1.3b {
  execsql {SELECT b from t1 where a = (SELECT a FROM t1 WHERE b=4)}
} {4}
do_test subselect-1.3c {
  execsql {SELECT b from t1 where a = (SELECT a FROM t1 WHERE b=6)}
} {6}
do_test subselect-1.3c {
  execsql {SELECT b from t1 where a = (SELECT a FROM t1 WHERE b=8)}
} {}

# What if the subselect doesn't return any value.  We should get
# NULL as the result.  Check it out.
#
do_test subselect-1.4 {
  execsql {SELECT b from t1 where a = coalesce((SELECT a FROM t1 WHERE b=5),1)}
} {2}

# Try multiple subselects within a single expression.
#
do_test subselect-1.5 {
  execsql {
    CREATE TABLE t2(x int, y int);
    INSERT INTO t2 VALUES(1,2);
    INSERT INTO t2 VALUES(2,4);
    INSERT INTO t2 VALUES(3,8);
    INSERT INTO t2 VALUES(4,16);
  }
  execsql {
    SELECT y from t2 
    WHERE x = (SELECT sum(b) FROM t1 where a notnull) - (SELECT sum(a) FROM t1)
  }
} {8}

# Try something useful.  Delete every entry from t2 where the
# x value is less than half of the maximum.
#
do_test subselect-1.6 {
  execsql {DELETE FROM t2 WHERE x < 0.5*(SELECT max(x) FROM t2)}
  execsql {SELECT x FROM t2 ORDER BY x}
} {2 3 4}

finish_test