从 SQL 中的多个相同格式的表中聚合数据

Question

I have 5 simple tables, that are all the same format. Eg: Table 1:

Color	Count
Blue	1
Red	2

Table 2:

Color	Count
Blue	0
Red	9

Table 3:

Color	Count
Blue	3
Red	1

etc.

What is an efficient SQL query to aggregate the data from all these tables with the same format? Desired output:

Color	Count
Blue	4
Red	12

My current idea is to simply join these tables on "Color", and then sum together the values from each column:

Color	Table 1 Count	Table 2 Count	Table 3 Count
Blue	1	0	3
Red	2	9	1

SELECT Color, (Table 1 Count + Table 2 Count + Table 3 Count) as Count:

Color	Count
Blue	4
Red	12

I know there must be a more efficient way to do this without having to join by color first. How can this be done?

Answer 1

Union works faster:

SELECT Color, sum(Count) 
FROM (
SELECT Color, Count FROM Table 1 
UNION ALL
SELECT Color, Count FROM Table 2 
UNION ALL
SELECT Color, Count FROM Table 3 
) t
GROUP BY Color