MySQL作為一款常用的關系型數據庫軟件，擁有很強的查詢和分析功能，能夠處理數百萬的電商大數據。在電商大數據查詢中，有以下幾種常見的方法：

1. 雙表聯查
SELECT t1.column1, t1.column2, t2.column1, t2.column2
FROM table1 AS t1
LEFT JOIN table2 AS t2
ON t1.common_column = t2.common_column
WHERE t1.condition1 = 'value1'
AND t2.condition2 = 'value2';
2. 子查詢
SELECT *
FROM table1
WHERE common_column IN
(SELECT common_column
FROM table2
WHERE condition = 'value');
3. 聚合函數
SELECT MAX(sale_amount), MIN(sale_amount), AVG(sale_amount)
FROM sale_table
WHERE sale_date BETWEEN '2018-01-01' AND '2019-12-31';
4. 多表聯查
SELECT t1.column1, t2.column2, t3.column3
FROM table1 AS t1
LEFT JOIN table2 AS t2
ON t1.common_column = t2.common_column
LEFT JOIN table3 AS t3
ON t2.common_column = t3.common_column
WHERE t1.condition1 = 'value1'
AND t2.condition2 = 'value2'
AND t3.condition3 = 'value3';

以上查詢方法僅是電商大數據查詢的冰山一角，在實際操作中還需結合實際業務需求，運用索引優化、分區查詢等方法，才能夠更好地處理電商大數據。