5.4.1 查询已用编号分布情况的示例（子查询法).sql

sqlserver 数据库编程的绝好脚本

--测试数据
CREATE TABLE tb(col1 varchar(10),col2 int)
INSERT tb SELECT 'a',2
UNION ALL SELECT 'a',3
UNION ALL SELECT 'a',6
UNION ALL SELECT 'a',7
UNION ALL SELECT 'a',8
UNION ALL SELECT 'b',3
UNION ALL SELECT 'b',5
UNION ALL SELECT 'b',6
UNION ALL SELECT 'b',7
GO

--已用编号分布查询
SELECT col1,start_col2=col2,
	end_col2=(
		SELECT MIN(col2) FROM tb aa
		WHERE col1=a.col1 AND col2>=a.col2 
			AND NOT EXISTS(
				SELECT * FROM tb WHERE col1=aa.col1 AND col2=aa.col2+1))
FROM tb a
WHERE NOT EXISTS(
	SELECT * FROM tb WHERE col1=a.col1 and col2=a.col2-1)
/*--结果
col1       start_col2  end_col2    
-------------- -------------- ----------- 
a          2           3
a          6           8
b          3           3
b          5           7
--*/