1、返回比较表达式如60 < 70的函数
函数f_exp_compare
//====================================================================
// 函数: f_exp_compare
//--------------------------------------------------------------------
// 描述: 返回比较表达式的结果
//--------------------------------------------------------------------
// 参数:
// value string as_str 表达式，如 60 < 70
//--------------------------------------------------------------------
// 返回值: string 比较表达试的结果 1为真，0为假，-1为表达式错误
//====================================================================
String ls_Ret
DataStore lds_Evaluate
lds_Evaluate = CREATE DataStore
lds_Evaluate.Create('release 8;~r~ntable()')
ls_Ret = lds_Evaluate.Describe("Evaluate('" + "if(" + as_str + ", 1, 0)" + "', 1)")
DESTROY lds_Evaluate
IF ls_Ret = '!' THEN ls_Ret = '-1'
RETURN ls_Ret
示例：
String ls_Exp, ls_Ret
ls_Exp = '60 < 70'
ls_Ret = f_exp_compare(ls_Exp)
MessageBox('', ls_Exp + ' --> ' + ls_Ret )
2、返回计算表达式如2 * (3+5) + 2^3的函数
//====================================================================
// 函数: f_exp_ret
//--------------------------------------------------------------------
// 描述: 返回计算表达式的值
//--------------------------------------------------------------------
// 参数:
// value string as_str 计算表达式，如 2 * (3+5) + 2^3
//--------------------------------------------------------------------
// 返回值: string 计算表达式的结果值，如果表达式不正确，返回'FALSE'
//====================================================================
String ls_Ret
DataStore lds_Evaluate
lds_Evaluate = CREATE DataStore
lds_Evaluate.Create('release 8;~r~ntable()')
ls_Ret = lds_Evaluate.Describe("Evaluate('" + as_str + "', 1)")
DESTROY lds_Evaluate
IF ls_Ret = '' OR ls_Ret = '!' THEN ls_Ret = 'FALSE'
RETURN ls_Ret
示例：
String ls_Exp, ls_Ret
ls_Exp = '60 * ( 1 + 3 ) + 2^3'
ls_Ret = f_exp_ret(ls_Exp)
MessageBox('', ls_Exp + ' --> ' + ls_Ret )
3、下面是收藏的在SQL中返回计算表达式的函数，但只能算加、减、乘、除，不能算幂：
CREATE FUNCTION dbo.GetExp(@pstrExpress AS VARCHAR(8000))
RETURNS DECIMAL(18,6) AS
BEGIN
DECLARE @i INT,@j INT
DECLARE @c1 CHAR(1),@c2 CHAR(1),@c VARCHAR(100)
DECLARE @v1 DECIMAL(18,6),@v2 DECIMAL(18,6),@v DECIMAL(18,6)
DECLARE @t TABLE(ID INT IDENTITY(1,1),s VARCHAR(100))
DECLARE @s TABLE(ID INT IDENTITY(1,1),s VARCHAR(100))
DECLARE @sv TABLE(ID INT IDENTITY(1,1),v DECIMAL(18,6))
SET @pstrExpress = REPLACE(@pstrExpress,' ','')
SELECT @i = 0,@j = LEN(@pstrExpress),@c2 = '',@c = ''
WHILE @i<@j
BEGIN
SELECT @c1 = @c2,@i = @i+1
SELECT @c2 = SUBSTRING(@pstrExpress,@i,1)
IF CHARINDEX(@c2,'.0123456789') > 0 or (@c2 = '-' and @c1 IN('','*','-','+','/','('))
BEGIN SELECT @c = @c + @c2 CONTINUE END
IF @c <> '' BEGIN INSERT @t(s) SELECT @c SELECT @c = '' END
IF CHARINDEX(@c2,')')>0
BEGIN
INSERT @t(s) SELECT s FROM @s WHERE ID > ISNULL((SELECT MAX(ID) FROM @s WHERE s IN('(')),0) ORDER BY ID DESC
DELETE @s WHERE ID >= ISNULL((SELECT MAX(ID) FROM @s WHERE s IN('(')),0)
CONTINUE
END
IF CHARINDEX(@c2,'+-)')>0
BEGIN
INSERT @t(s) SELECT s FROM @s WHERE ID > ISNULL((SELECT MAX(ID) FROM @s WHERE s IN('(')),0) ORDER BY ID DESC
DELETE @s WHERE ID > ISNULL((SELECT MAX(ID) FROM @s WHERE s IN('(')),0)
IF @c2 <> ')' INSERT @s(s) SELECT @c2
CONTINUE
END
IF CHARINDEX(@c2,'*/')>0
BEGIN
INSERT @t(s) SELECT s FROM @s WHERE ID > ISNULL((SELECT MAX(ID) FROM @s WHERE s IN('(','+','-')),0) ORDER BY ID DESC
DELETE @s WHERE ID > ISNULL((SELECT MAX(ID) FROM @s WHERE s IN('(','+','-')),0)
INSERT @s SELECT @c2
CONTINUE
END
IF CHARINDEX(@c2,'(')>0 INSERT @s SELECT @c2
END
IF @c <> '' INSERT @t(s) SELECT @c
INSERT @t(s) SELECT s FROM @s ORDER BY ID DESC
SELECT @i = 0,@j = MAX(ID) FROM @t
WHILE @i < @j
BEGIN
SELECT @i = @i + 1
SELECT @c = s FROM @t WHERE ID = @i
IF @c = '(' CONTINUE
IF @c NOT IN('*','-','+','/') BEGIN INSERT @sv(v) SELECT CONVERT(float,@c) CONTINUE END
SELECT @v2 = v FROM @sv DELETE @sv WHERE ID = (SELECT MAX(ID) FROM @sv)
SELECT @v1 = v FROM @sv DELETE @sv WHERE ID = (SELECT MAX(ID) FROM @sv)
SELECT @v = CASE @c WHEN '+' THEN @v1 + @v2 WHEN '-' THEN @v1 - @v2
WHEN '*' THEN @v1 * @v2 WHEN '/' THEN @v1 / @v2 END
INSERT @sv(v) SELECT @v
END
SELECT @v = v FROM @sv
RETURN @v
END
示例：
SELECT dbo.GetExp('60 * ( 1 + 3 )')
/*结果
--------------------
240.000000
（所影响的行数为 1 行）
*/
