使用SQL Server 2008中的条件更新行

This is my table structure:

这是我的表格结构:

CREATE table Credit(id integer, organisationid int, availableCredit int)

INSERT INTO Credit VALUES (1, 1, 1000)
INSERT INTO Credit VALUES (2, 1, 100)
INSERT INTO Credit VALUES (3, 2, 600)
INSERT INTO Credit VALUES (4, 2, 400)
CREAT