Question

您好我正在努力创造一些东西，但我的总数不是负数。所以基本上我得到的是负值，可以乘以一个有点复杂的数学方程。

所以......用户输入的数据从-1到1.（-1,0,1）它会在我的公式中成倍增加。所以我的SQL查询看起来像这样......（这部分有效！）

SELECT *, a, b, c AS TOTALNUMBER FROM MATH
ORDER BY TOTALNUMBER DESC

但是，我需要总数为正数。所以我在过去的几个小时里一直试图解决这个问题。我是php / sql的新手。

我想尝试包括......

if (TOTALNUMBER < 0 ) {
TOTALNUMBER * -1.0
}

但是我不知道在查询中包含这个内容或者如何正确编写它。

澄清和更新我要找的东西...... 用户可以输入-1,0,1

例如，A，B，C的数据。 10,15,20 用户输入：1，-1,0

A total = 10
B total = -15
C total = 0
Total ABC = -5

但是，我需要总数为5而不是-5而不更改任何A，B，C值。

Answer 1

use like this

SELECT *, a, b, ABS(c) AS TOTALNUMBER FROM MATH
ORDER BY TOTALNUMBER DESC

Answer 2

IF(expr1,expr2,expr3)

If expr1 is TRUE (expr1 <> 0 and expr1 <> NULL) then IF() returns expr2; otherwise it returns expr3. IF() returns a numeric or string value, depending on the context in which it is used.

SELECT a, b, c, If (c <0 , c * -1, c) AS TOTALNUMBER FROM MATH
ORDER BY TOTALNUMBER DESC;

If you want the sum of all the fields to be your total number, assuming you have an id field:

SELECT a,b,c,ABS((sum(a)+(b)+(c))) AS TOTALNUMBER FROM MATH
group by mathid ORDER BY TOTALNUMBER DESC;

Here is an example:

mysql> select * from math;
+--------+----------+
| idmath | mathcol1 |
+--------+----------+
|      1 |        1 |
|      2 |        3 |
|      3 |       -1 |
|      4 |       -3 |
+--------+----------+
4 rows in set (0.00 sec)

mysql> SELECT idmath, If (mathcol1 <0 , mathcol1 * -1, mathcol1) AS TOTALNUMBER
FROM MATH ORDER BY TOTALNUMBER DESC;
+--------+-------------+
| idmath | TOTALNUMBER |
+--------+-------------+
|      2 |           3 |
|      4 |           3 |
|      1 |           1 |
|      3 |           1 |
+--------+-------------+
4 rows in set (0.00 sec)

mysql> SELECT idmath, mathcol1, If (mathcol1 <0 , mathcol1 * -1, mathcol1) AS TO
TALNUMBER FROM MATH ORDER BY TOTALNUMBER DESC;
+--------+----------+-------------+
| idmath | mathcol1 | TOTALNUMBER |
+--------+----------+-------------+
|      2 |        3 |           3 |
|      4 |       -3 |           3 |
|      1 |        1 |           1 |
|      3 |       -1 |           1 |
+--------+----------+-------------+
4 rows in set (0.00 sec)

mysql> SELECT mathcol1,mathcol2,mathcol3, (sum(ABS(mathcol1))+(mathcol2)+(mathco
    l3)) AS TOTALNUMBER FROM MATH group by idmath ORDER BY TOTALNUMBER DESC;
    +----------+----------+----------+-------------+
    | mathcol1 | mathcol2 | mathcol3 | TOTALNUMBER |
    +----------+----------+----------+-------------+
    |        3 |        2 |        3 |           8 |
    |       -3 |        2 |        3 |           8 |
    |       -1 |        2 |        3 |           6 |
    |        1 |        2 |        3 |           6 |
    +----------+----------+----------+-------------+
    4 rows in set (0.00 sec)

You can read more here at dev.mysql.

PHP / SQL：如果查询中有语句？

2 个答案: