1.mysql加减乘除操作：mysql> select score,score+5,score-5,score*5,score/5 from 4a;
+——-+———+———+———+———+
| score | score+5 | score-5 | score*5 | score/5 |
+——-+———+———+———+———+
| 93 | 98 | 88 | 465 | 18.6000 |
| 35 | 40 | 30 | 175 | 7.0000 |
| 46 | 51 | 41 | 230 | 9.2000 |
| 56 | 61 | 51 | 280 | 11.2000 |
| 79 | 84 | 74 | 395 | 15.8000 |
| 91 | 96 | 86 | 455 | 18.2000 |
| 53 | 58 | 48 | 265 | 10.6000 |
| 56 | 61 | 51 | 280 | 11.2000 |
| 58 | 63 | 53 | 290 | 11.6000 |
| 68 | 73 | 63 | 340 | 13.6000 |
| 71 | 76 | 66 | 355 | 14.2000 |
| 93 | 98 | 88 | 465 | 18.6000 |
| 67 | 72 | 62 | 335 | 13.4000 |
| 78 | 83 | 73 | 390 | 15.6000 |
| 88 | 93 | 83 | 440 | 17.6000 |
| 90 | 95