要按salesrep保持数据在行上对齐，那么您仍然需要添加所有的数字-但是您可以在它们超出范围的地方用零替换。。。。

SUM(IF (order_closed BETWEEN '2020-11-01' AND '2020-11-30', lines_total, 0)) AS OTLMSUM

您指出出现语法错误，但这看起来像是语义错误：

SUM(order_type = 'NEW') OTNEW

你真的想把这些加起来吗？数一数？把它们分类？
查询可能类似于。。。

SELECT salesrep, 
    SUM(lines_total) AS OTSUM,
    SUM(IF(order_type = 'NEW', 1, 0)) OTNEW,
    SUM(IF(order_type = 'REPEAT', 1, 0)) OTREPEAT,
    SUM(IF (order_closed BETWEEN '2020-11-01' AND '2020-11-30', lines_total, 0)) AS OTLMSUM
    SUM(if(order_closed BETWEEN '2020-12-01' AND '2020-12-31', lines_total, 0)) AS OTTMSUM
FROM `ranger_orders`
WHERE order_closed BETWEEN '2020-01-01' AND '2020-12-31'

另外，对于聚合查询（sum、average、count…），应该有一个groupby子句。。。。

GROUP BY salesrep

然而，这样做不是更简单吗。。。。

SELECT salesrep, 
    SUM(lines_total) AS OTSUM,
    SUM(IF(order_type = 'NEW', 1, 0)) AS OTNEW,
    SUM(IF(order_type = 'REPEAT', 1, 0)) AS OTREPEAT,
    DATE_FORMAT(order_closed, '%Y-%m') AS month,
    SUM(lines_total) AS otsum
FROM `ranger_orders`
WHERE order_closed BETWEEN '2020-01-01' AND '2020-12-31'
GROUP BY salesrep, DATE_FORMAT(order_closed, '%Y-%m')

你需要 CASE 条件聚合的表达式，如：

SUM(CASE WHEN order_closed BETWEEN '2020-12-01' AND '2020-12-31' THEN lines_total ELSE 0 END) AS OTTMSUM

对于每一个和，改变 BETWEEN '2020-12-01' AND '2020-12-31' 相应地。