表记录某个字段中如何最高效率的取得最大值？难。。。

好记忆不如烂笔头abc 2014-12-19 04:26:42

例如表a中有个字段demo内容如下：
记录1：713:144,706:142,699:139,691:138,687:136,683:134,679:131,675:130,672:128,670:127,667:127,665:127,663:127,661:126,659:126,657:125,655:125,654:125,652:125,650:126,601:160,600:163,599:165,598:168,596:176,597:172,592:185,590:188,590:190,588:190,588:192,588:192,588:196,588:194,589:198,592:211,590:199,591:200,592:203,592:206,592:208,592:204,592:210,592:214,592:215,592:217,592:218,590:220,590:221,589:224,589:225,588:226,588:228,587:228,586:229,585:230,585:231,585:234,583:234,583:235,582:236,579:238,575:241,571:244,568:248,556:257,563:252,527:268,543:264,538:266,533:267,521:270,507:273,501:273,496:273,490:273,483:273,478:273,468:273,456:271,450:270,443:269,436:266,428:265,422:264,415:261,407:259,401:255,395:253,389:250,374:245,383:248,367:244,363:243,360:242,357:242,352:241,350:241,342:240,339:239,336:237,330:234,322:231,318:227,315:225,313:224,307:221,306:219,310:222,312:223,309:221,304:219,303:218,302:218,301:218,301:217,300:217,298:217,297:217,289:217,294:217,292:217,286:217,284:217,282:217,280:217,275:217,274:217,272:217,271:217,269:217,266:217,264:217,262:217,261:217,260:217,259:217,258:217,257:217,256:217,252:217,251:217,250:217,249:217,246:217,245:217,244:217,242:217,241:217,239:217,238:217,238:218,237:218,236:218,235:218,234:218,232:218,231:218,229:219,177:252,227:220,226:221,221:222,216:222,209:224,197:231,191:235,187:241,181:247,172:257,170:261,163:266,153:278,157:271,147:284,141:291,131:303,124:315,118:324,120:320,114:331,112:335,111:337,111:339,110:345,110:346,110:343,110:348,110:347,109:349,109:350,108:350,107:350,106:350,41:296,105:350,104:350,101:349,94:344,97:347,89:340,85:336,80:332,75:328,64:319,69:324,54:307,59:313,47:302,36:289,29:282,32:285,27:279,25:277,25:275,25:274,25:273,25:271,25:269,25:267,25:266,25:262,26:261,88:195,27:259,27:257,28:256,29:254,30:252,32:249,34:246,37:243,40:239,50:229,45:234,57:223,90:193,63:216,69:211,74:207,78:204,84:199,86:198,87:196,91:193,92:191,93:190,95:190,94:190,97:190,104:190,109:190,100:190,113:190,118:190,131:191,123:190,230:200,136:192,145:193,152:193,159:195,167:196,175:196,184:197,191:198,200:199,209:199,217:200,240:203,250:204,273:204,311:207,287:204,299:206,329:210,344:212,338:211,349:213,352:214,356:215,358:215,360:215,364:215,362:215,367:216,369:216,371:216,373:216,375:216,377:216,382:216,387:216,389:216,392:216,395:216,397:216,399:216,402:216,409:216,414:216,421:216,430:216,439:216,579:216,489:216,462:216,518:216,534:216,554:216,604:216,629:216,660:216,685:216,882:221,719:216,774:216,895:222,908:223,828:216,867:220,920:226,934:226,945:226,968:226,957:226,980:226,988:227,994:227,1001:227,1009:225,1005:226,1011:223,1013:221,1013:220,1013:217,1013:215,1013:214,1013:212,1013:211,1013:206,1013:202,1013:201,1013:199,1013:198,1013:196,1014:195,1015:194,1016:191,1019:186,1022:181,1024:173,1025:159,1025:144,1025:151,1025:135,1023:129,1021:122,1018:116,1011:108,1015:113,994:92,999:95,1009:104,988:87,981:82,973:76,960:71,945:65,928:59,881:45,909:54,851:39,827:34,794:29,768:26,739:24,711:23,689:23,640:21,607:21,594:21,581:21,553:21,571:21,540:21,533:21,526:21,519:21,515:21,501:21,490:21,483:21,476:21,469:21,463:21,455:21,448:21,442:21,433:21,425:21,418:22,383:26,375:28,393:26,410:22,365:29,355:30,348:32,340:34,308:44,317:41,301:45,287:48,294:47,281:49,324:39,273:52,278:51,268:54,265:54,262:55,259:56,261:55,253:57,246:60,248:59,243:61,237:61,231:63,225:65,221:66,215:67,205:70,192:75,198:73,186:77,184:77,188:76,182:78,179:79,177:81,173:85,175:83,160:88,171:86,154:88,150:88,144:90,137:90,131:91,124:92,118:93,111:94,103:96,97:98,92:100,86:102,82:104,77:106,68:110,65:112,64:113,63:114,62:115,61:116,60:116,60:117,59:118,57:119,58:119,55:121,54:121,56:120,50:121,52:121,48:121,46:121,45:121,40:120,38:120,33:117,30:116,30:113,27:112,24:109,21:107,21:106,19:106,19:105,18:105,18:104,18:103,18:102,17:101,17:100,16:100,17:100,15:100,15:99,15:99,15:99,15:99,15:99,15:99,15:99,18:99,20:98,23:97,24:97,27:96,28:96,30:96,30:95,31:95,32:95,32:94,31:94,30:94,28:94,29:94,27:96,27:98,27:100,27:102,27:105,27:110,27:109,27:107,27:113,27:116,27:115,28:118,28:119,29:121,30:124,31:126,33:128,33:128,35:131,42:140,48:144,53:149,60:154,66:160,73:165,81:170,87:174,94:178,99:182,104:187,108:190,112:194,114:198,122:206,117:201,126:212,148:234,143:229,131:217,154:239,165:247,167:249,173:252,175:253,176:253,177:253,177:251,177:250,178:247,180:243,181:240,183:232,183:224,183:219,183:213,183:207,183:203,184:199,184:195,184:192,184:190,184:191,185:190,186:190,187:189,188:189,189:189,186:189,191:189,192:189,193:189,194:189,196:189,203:190,197:189,206:190,210:191,221:191,229:191,232:191,236:191,239:191,247:192,243:192,260:194,276:197,285:201,295:202,306:205,446:272,341:211,359:216,377:226,385:230,393:235,402:241,418:251,432:260,424:256,438:265,443:269,445:271,317:206,447:272,447:273,447:268,447:272,446:263,444:261,442:257,439:254,436:250,422:238,431:245,415:231,409:225,405:221,403:219,400:217,391:210,394:212,383:206,386:208,380:205,375:203,372:203,370:202,369:201,366:200,368:200,365:198,364:198,364:196,363:196,362:195,362:194,360:201,360:207,360:211,360:214,362:219,363:222,366:226,368:232,401:281,371:236,376:244,382:251,390:260,396:271,409:294,417:304,425:316,433:327,442:336,458:353,471:364,477:370,481:373,484:376,489:378,466:178,459:178,456:178,455:178,451:178,446:176,445:174,448:178,435:167,426:163,421:161,418:159,413:157,410:156,408:155,404:153,402:152,401:151,401:152,400:150,399:150,397:147,394:145,392:143,391:143,391:142,391:141,391:140,391:139,390:137,390:138,390:137,392:137,391:137,398:137,402:137,405:138,415:141,432:144,467:149,522:155,570:163,594:167,612:170,638:171,501:152,663:173,675:174,700:178,723:186,735:189,748:195,763:202,778:210,807:224,834:241,888:272,863:256,904:279,933:298,954:317,961:322,968:326,977:335,982:338,949:310,991:348,1001:357,1007:362,1013:368,1020:377,1024:386,1031:397,1038:408,1051:435,1062:455,1281:650,1284:650,1288:653,1068:467,1291:654,957:440,1026:454,1015:452,990:447,943:436,919:428,931:432,910:425,896:419,892:415,891:415,891:411,891:413,891:410,893:408,886:395,895:405,878:388,857:368,849:361,839:353,833:348,824:343,801:332,788:325,772:317,751:304,724:291,698:279,633:249,605:237,573:225,552:214,524:201,513:194,503:189,496:186,482:179,474:173,468:168,460:163,488:182,456:161,465:167,454:159,452:154,444:148,438:143,430:139,410:128,417:131,423:134,405:126,402:125,401:125,399:126,398:128,398:130,398:131,398:132,398:133,397:133,396:133,395:133,395:133,395:133,395:133,396:133,408:136,434:144,484:165,516:181,546:197,580:211,623:231,663:250,715:275,769:304,820:327,880:354,916:377,985:412,1051:448,1080:462,1313:653,1314:654,1206:369,1172:329,1156:313,1144:301,1181:339,1137:291,1138:293,1135:289,1135:288,1135:287,1133:285,1132:284,1132:281,1130:277,1128:274,1127:269,1121:257,1109:237,1118:251,1101:228,1093:219,1074:199,1062:191,1050:180,1026:162,1002:144,992:138,968:125,948:115,933:108,923:105,920:104,917:102,915:101,915:100,914:100,913:100,902:101,889:101,873:102,896:101,843:109,832:110,818:113,789:117,730:129,770:121,677:145,647:152,619:160,541:173,563:168,515:179,495:182,484:183,478:183,473:183,469:183,467:183,466:182,461:180,471:183,458:178,449:168,451:170,445:164,442:163,433:155,436:158,430:153,427:152,426:150,424:149,422:148,420:147,415:144,412:143,410:141,408:141,406:140,405:139,404:139,401:138,399:138,398:137,397:137,396:136,395:136,393:136,390:134,391:135,390:134,392:135,390:134,395:133,401:133,413:133,418:133,431:134,437:136,444:137,451:138,458:139,465:139,473:139,481:140,496:140,505:141,565:154,520:142,548:146,528:143,587:164,598:169,608:177,621:184,636:195,651:203,670:215,715:236,803:276,745:250,860:300,921:324,968:346,1009:368,1066:408,1080:417,1102:435,1035:388,1112:443,1134:460,1148:474,1162:487,1175:502,1187:517,1200:534,1297:619,1213:548,1219:554,1226:562,1238:572,1243:577,1262:591,1256:586,1273:601,1281:607,1290:614,1300:622,1304:624,1307:626,1312:628,1314:631,1314:633,1313:630,1314:635,1311:641,1314:634,1309:642,1305:646,1304:649,1303:651,1301:653

记录2：843:109,832:110,818:113,789:117,730:129,770:121,677:145,647:152,619:160,541:173,563:168,515:179,495:182,484:183,478:183,473:183,469:183,467:183,466:182,461:180,471:183,458:178,449:168,451:170,445:164,442:163,433:155,436:158,430:153,427:152,426:150,424:149,422:148,420:147,415:144,412:143,410:141,408:141,406:140,405:139,404:139,401:138,399:138,398:137,397:137,396:136,395:136,393:136,390:134,391:135,390:134,392:135,390:134,395:133,401:133,413:133,418:133,431:134

记录3：
391:140,391:139,390:137,390:138,390:137,392:137,391:137,398:137,402:137,405:138,415:141,432:144,467:149,522:155,570:163,594:167,612:170,638:171,501:152,663:173,675:174,700:178,723:186,735:189,748:195,763:202,778:210,807:224,834:241,888:272,863:256,904:279,933:298,954:317,961:322,968:326,977:335,982:338,949:310,991:348,1001:357,1007:362,1013:368,1020:377,1024:386,1031:397,1038:408,1051:435,1062:455,1281:650,1284:650,1288:653,1068:467,1291:654,957:440,1026:454,1015:452,990:447,943:436,919:428,931:432,910:425,896:419,892:415,891:415,891:411,891:413,891:410,893:408,886:395,895:405,878:388,857:368,849:361,839:353,833:348,824:343,801:332,788:325,772:317,751:304,724:291,698:279,633:249,605:237,573:225

该字段可能还有更多记录。。。

如何快速取得该字段demo中所有记录中冒号：右边的最大值：
当前结果为654

怎样的SQL效率最高？谢谢！

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