關於Java中SQL語句的拼接規則

實現目標語句是這個
注意，這里的java變量是idd

int idd;
String sql = "SELECT id, piUrl FROM picinfos WHERE id BETWEEN  '" + idd + "' AND 10" ;

java中的字符串只能雙引號，如果字符串中需要拼接變量，該變量用單引號括起來，然后加兩個雙引號再加兩個加號，中間就是變量。

拼接步驟

1. 寫出SQL具體語句（無變量都是具體值的），比如上面的sql

   //查詢picinfos表中id為2到10的id和piUrl值
   String sql = "SELECT id, piUrl FROM picinfos WHERE id BETWEEN  2 AND 10" ;

   2.此時要將2改為id（int類型變量），只需要在中間修改
   ，先是刪掉2，用單引' '代替

   String sql = "SELECT id, piUrl FROM picinfos WHERE id BETWEEN  '  ' AND 10" ;

   3.接着在單引號中間加上雙引" "

   String sql = "SELECT id, piUrl FROM picinfos WHERE id BETWEEN  ' "    " ' AND 10" ;

   4.接着在雙引號中間加上加號+ +

   String sql = "SELECT id, piUrl FROM picinfos WHERE id BETWEEN  ' " +  + " ' AND 10" ;

   5.最后就是加號中間加上變量idd完事

   String sql = "SELECT id, piUrl FROM picinfos WHERE id BETWEEN  ' " + idd + " ' AND 10" ;

   口訣：先SQL原型，替換為單引，中間加雙引，中間加雙加號，中間加變量。