SUBSTR和INSTR SQL Oracle [英] SUBSTR and INSTR SQL Oracle

问题描述

我已经开始在Oracle中使用SUBSTR和INSTR，但是遇到这个问题时我感到困惑.

I've started using SUBSTR and INSTR in Oracle but I got confused when I came across this.

SELECT PHONE, SUBSTR(PHONE, 1, INSTR(PHONE, '-') -1)
FROM DIRECTORY;

所以我知道SUBSTR切断了值，而INSTR显示了发生的位置，但是我上面举的示例使我感到困惑，因为结果为362.当我的原始值为362-127-4285时.这是如何运作的?

So I know SUBSTR cuts values off, and INSTR shows where the occurrence is but the example I've put above has confused me, because the result it 362. When my original value was 362-127-4285. How does that work?

推荐答案

INSTR(PHONE，'-')给出-的 index >在 PHONE 列中，以您的情况为 4
然后是 SUBSTR(PHONE，1，4-1)或 SUBSTR(PHONE，1，3)
从 1st 给出 PHONE 列的 substring ，其长度为 3 个字符，即 362，
如果 PHONE 列的值为 362-127-4285 .

INSTR(PHONE, '-') gives the index of - in the PHONE column, in your case 4
and then SUBSTR(PHONE, 1, 4 - 1) or SUBSTR(PHONE, 1, 3)
gives the substring of the PHONE column from the 1st that has length of 3 chars which is 362,
if the value PHONE column is 362-127-4285.

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