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Hello guys. Please do me a favor and help me solve this slow query Tables: CREATE TABLE `products` ( `ProductId` int(11) NOT NULL AUTO_INCREMENT, `CategoryId` int(11) NOT NULL, `BrandId` int(11) DEFAULT NULL, `PCode` varchar(100) COLLATE utf8_persian_ci NOT NULL, `PName` varchar(255) COLLATE utf8_persian_ci NOT NULL, `UnitId` int(11) DEFAULT NULL, `PNameEn` varchar(250) COLLATE utf8_persian_ci DEFAULT NULL, `PShortName` varchar(100) COLLATE utf8_persian_ci DEFAULT NULL, `PDescription` varchar(250) COLLATE utf8_persian_ci DEFAULT NULL, `Weight` int(11) DEFAULT NULL, `PImage` varchar(100) COLLATE utf8_persian_ci NOT NULL DEFAULT 'noimage.png', `PIcon` varchar(100) COLLATE utf8_persian_ci DEFAULT 'noicon.png', `PGallery` varchar(250) COLLATE utf8_persian_ci DEFAULT NULL, `PDetail` text COLLATE utf8_persian_ci, `PTags` text COLLATE utf8_persian_ci, `PSpecial` tinyint(4) NOT NULL DEFAULT '0', `PView` int(11) NOT NULL DEFAULT '0', `Status` tinyint(2) DEFAULT '1' COMMENT '0: inactive. 1: active. 5: deleted.', `BasePrice` int(11) DEFAULT NULL, `PCreateDate` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP, `PUpdateDate` datetime NOT NULL, `PUrl` varchar(255) COLLATE utf8_persian_ci DEFAULT NULL, `ProviderName` varchar(255) COLLATE utf8_persian_ci DEFAULT NULL, PRIMARY KEY (`ProductId`), UNIQUE KEY `PCode` (`PCode`), KEY `CategoryId` (`CategoryId`), KEY `BrandId` (`BrandId`), KEY `PName` (`PName`) ) ENGINE=MyISAM AUTO_INCREMENT=341028 DEFAULT CHARSET=utf8 COLLATE=utf8_persian_ci CREATE TABLE `units` ( `UnitId` int(11) NOT NULL AUTO_INCREMENT, `UnitName` varchar(25) COLLATE utf8_persian_ci NOT NULL, PRIMARY KEY (`UnitId`) ) ENGINE=MyISAM AUTO_INCREMENT=22 DEFAULT CHARSET=utf8 COLLATE=utf8_persian_ci CREATE TABLE `products_sub` ( `ProductSubId` int(11) NOT NULL AUTO_INCREMENT, `ProviderId` int(11) NOT NULL, `PCode` varchar(100) COLLATE utf8_persian_ci NOT NULL, `Price` int(11) NOT NULL, `ProviderPrice` int(11) NOT NULL, `PQuantity` int(10) NOT NULL, `PDeliveryTime` time NOT NULL, `PEditTime` datetime DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, PRIMARY KEY (`ProductSubId`), KEY `ProviderId` (`ProviderId`), KEY `PCode` (`PCode`) ) ENGINE=MyISAM AUTO_INCREMENT=340349 DEFAULT CHARSET=utf8 COLLATE=utf8_persian_ci CREATE TABLE `provider` ( `ProviderId` int(11) NOT NULL AUTO_INCREMENT, `UserId` int(11) NOT NULL, `ProviderName` varchar(25) COLLATE utf8_persian_ci NOT NULL, `ProviderPhone` varchar(11) COLLATE utf8_persian_ci NOT NULL, `ProviderCell` varchar(11) COLLATE utf8_persian_ci NOT NULL, `ProviderAddress` varchar(250) COLLATE utf8_persian_ci NOT NULL, `ProviderDetail` text COLLATE utf8_persian_ci NOT NULL, `Email` varchar(50) COLLATE utf8_persian_ci NOT NULL, `Status` tinyint(1) NOT NULL, `RequestTime` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP, `Permission` varchar(250) COLLATE utf8_persian_ci NOT NULL, PRIMARY KEY (`ProviderId`), UNIQUE KEY `UserId` (`UserId`) ) ENGINE=MyISAM AUTO_INCREMENT=2 DEFAULT CHARSET=utf8 COLLATE=utf8_persian_ci CREATE TABLE `order_products` ( `OrderProductId` int(11) NOT NULL AUTO_INCREMENT, `OrderId` int(11) NOT NULL, `ProviderId` int(11) NOT NULL, `PCode` varchar(50) COLLATE utf8_persian_ci NOT NULL, `PName` varchar(50) COLLATE utf8_persian_ci NOT NULL, `PUnit` varchar(50) COLLATE utf8_persian_ci NOT NULL, `Token` int(11) NOT NULL DEFAULT '999', `ProductPrice` int(11) NOT NULL, `ProductWeight` int(11) NOT NULL, `ProductPurchase` int(11) NOT NULL, PRIMARY KEY (`OrderProductId`), KEY `ProductId` (`PCode`), KEY `OrderId` (`OrderId`), KEY `ProviderId` (`ProviderId`) ) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=utf8 COLLATE=utf8_persian_ci CREATE TABLE `brands` ( `BrandId` int(11) NOT NULL AUTO_INCREMENT, `BrandName` varchar(25) NOT NULL, `BrandEn` varchar(25) DEFAULT NULL, PRIMARY KEY (`BrandId`), UNIQUE KEY `BrandName` (`BrandName`) ) ENGINE=MyISAM AUTO_INCREMENT=1988 DEFAULT CHARSET=utf8 My Query: SELECT `products`.`ProductId`, `products`.`PName`, `products`.`Status`, `products`.`PSpecial`, `products`.`PImage`, `products`.`BasePrice`, `products`.`CategoryId`, `units`.`UnitName`, `products_sub`.`ProductSubId`, `products_sub`.`ProviderId`, `products_sub`.`PQuantity`, `products_sub`.`ProviderPrice`, `products_sub`.`Price` AS `customerPrice`, `provider`.`ProviderName`, SUM(`order_products`.`ProductPurchase`) AS `sale` FROM `products` LEFT JOIN `brands` ON `products`.`BrandId`=`brands`.`BrandId` INNER JOIN `units` ON `products`.`UnitId`=`units`.`UnitId` LEFT JOIN `products_sub` ON `products`.`PCode`=`products_sub`.`PCode` AND `products_sub`.`ProductSubId` = ( SELECT `ProductSubId` FROM `products_sub` WHERE `PCode`=`products`.`PCode` AND `PQuantity` > 0 ORDER BY `ProviderPrice` LIMIT 1 ) LEFT JOIN `provider` ON `products_sub`.`ProviderId`=`provider`.`ProviderId` LEFT JOIN `order_products` ON `products`.`PCode`=`order_products`.`PCode` WHERE `products`.`Status`>0 AND `products`.`Status`!=5 AND `products`.`CategoryId` IN (1133,1134,1137,1174,1175,1176,1138,1177,1178,1179,1139,1140,1141,1180,1181,1182,1183,1184,1142,1143,1144,1145,1185,1186,1187,1188,1189,1190,1191,1146,1147,1148,1149,1150,1192,1193,1194,1855,1856,1857,1135,1151,1152,1153,1154,1155,1156,1157,1158,1136,1159,1160,1161,1162,1163,1164,1165,1166,1195,1196,1197,1198,1199,1167,1168,1200,1201,1202,1203,1204,1205,1169,1206,1207,1208,1209,1170,1171,1172,1173,1210,1211,1858,1859,1212,1213,1214,1232,1233,1234,1215,1216,1235,1236,1237,1238,1217,1239,1240,1241,1242,1218,1219,1220,1243,1244,1245,1246,1247,1248,1221,1249,1250,1251,1222,1223,1224,1252,1253,1254,1225,1255,1256,1257,1258,1259,1260,1261,1262,1263,1226,1227,1228,1229,1230,1231,1264,1265,1266,1267,1268,1269,1270,1271,1272,1273,1274,1275,1276,1277,1278,1279,1280,1281,1282,1283,1284,1285,1463,1464,1475,1476,1477,1478,1479,1480,1481,1482,1483,1484,1465,1466,1467,1485,1486,1487,1488,1489,1490,1491,1492,1493,1494,1468,1495,1496,1497,1498,1499,1500,1501,1502,1503,1504,1505,1506,1507,1469,1470,1471,1472,1473,1474,1508,1509,1286,1287,1290,1299,1395,1396,1300,1301,1397,1398,1399,1302,1303,1304,1305,1400,1401,1402,1306,1307,1308,1309,1403,1404,1310,1405,1406,1407,1408,1311,1312,1313,1314,1315,1409,1410,1291,1316,1317,1318,1319,1320,1292,1321,1322,1323,1324,1288,1293,1325,1411,1412,1326,1327,1413,1414,1328,1329,1330,1331,1415,1416,1417,1418,1332,1419,1420,1421,1422,1333,1334,1335,1423,1424,1336,1425,1426,1427,1428,1429,1430,1431,1337,1338,1432,1433,1434,1339,1340,1341,1342,1435,1436,1437,1343,1438,1439,1440,1441,1294,1344,1345,1346,1347,1348,1349,1350,1351,1352,1353,1295,1354,1355,1356,1357,1358,1359,1360,1361,1362,1363,1860,1861,1862,1289,1296,1364,1442,1443,1444,1365,1445,1446,1447,1448,1366,1367,1368,1369,1449,1450,1451,1452,1453,1370,1371,1372,1373,1454,1455,1456,1457,1458,1459,1374,1375,1460,1376,1377,1378,1379,1461,1462,1297,1380,1381,1382,1383,1384,1385,1386,1298,1387,1388,1389,1390,1391,1392,1393,1394,1863,1864,1865,1132) GROUP BY `products`.`PCode` ORDER BY `products`.`Status`, `products_sub`.`PQuantity` > 0 DESC, `products`.`PSpecial` DESC, `customerPrice` ASC, `products`.`BasePrice` ASC LIMIT 36 OFFSET 0 This query is extremely slow When is remove the ORDER BY section, It will run very fast. As i researched, its better to use sub-queries. but didn't figure out how to use them with left join. Any help is appreciated. thanks.

I've created a course utilization report which is made up of several different MySQL queries. As you know, if a row contains no data, the result is NULL. IFNULL works to combat that, but doesn't work if there is a GROUP BY clause (GROUP BY a.courseSection). So, I need to figure out how to get it to return zero when one of the rows is null. If you look at the line Average Student Drops in the screenshot, you see that there are two cells missing which is throwing off the data. For example, since 2015 is null, everything shifts to the left. Below is the query I am using; any help with this is greatly appreciated. SELECT AVG(drops) FROM ( SELECT IFNULL(COUNT(a.stuAcadCredID),0) as drops,YEAR(a.addDate) as year FROM stu_acad_cred a LEFT JOIN course_sec b ON a.courseSection = b.courseSection LEFT JOIN course c ON b.courseID = c.courseID WHERE a.status IN('D') GROUP BY a.courseSection ) stuDrops GROUP BY year DESC LIMIT 10