實(shí)現(xiàn)目標(biāo)語(yǔ)句是這個(gè)
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(hào)，如果字符串中需要拼接變量，該變量用單引號(hào)括起來(lái)，然后加兩個(gè)雙引號(hào)再加兩個(gè)加號(hào)，中間就是變量。
拼接步驟
- 寫(xiě)出SQL具體語(yǔ)句（無(wú)變量都是具體值的），比如上面的sql
//查詢(xún)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(shí)要將2改為id（int類(lèi)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.接著在單引號(hào)中間加上雙引" "
String sql = "SELECT id, piUrl FROM picinfos WHERE id BETWEEN ' " " ' AND 10" ;
4.接著在雙引號(hào)中間加上加號(hào)+ +
String sql = "SELECT id, piUrl FROM picinfos WHERE id BETWEEN ' " + + " ' AND 10" ;
5.最后就是加號(hào)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(hào)，中間加變量。
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