sqlserver中如何获取指标，求助各位大佬

sqlserver中如何写sql只匹配带有三个或者只带有四个‘+’字符串的计算公式，分别获取计算公式中的每个指标，感谢各位大佬

这个能满足要求不？

WITH x AS (/*示例数据*/
SELECT 'a1' AS zbm, 'b1' AS jsgs UNION ALL 
SELECT 'a2' AS zbm, 'b1+b2' AS jsgs UNION ALL 
SELECT 'a3' AS zbm, 'b1+b2+b3' AS jsgs  UNION ALL 
SELECT 'a4' AS zbm, 'b1+b2+b3+b4' AS jsgs 
)
SELECT zbm, jsgs
FROM x
WHERE len(jsgs) - len(replace(jsgs,'+',''))=3