Question

我有一个名为 value_record 的表格，如下所示

log4j.appender.DB=org.apache.log4j.jdbc.JDBCAppender
log4j.appender.DB.URL=jdbc:sqlserver://172.16.0.201:1433;databaseName=databaseone;autoReconnect=true
log4j.appender.DB.driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
log4j.appender.DB.user=username
log4j.appender.DB.password=password$123
log4j.appender.DB.sql=INSERT INTO usage_fact(accessed_date,accessed_item_id,user_id,tenant_id,log_level) VALUES('%d{yyyy-MM-dd HH:mm:ss}','%X{accessed_item_id}','%X{user_id}','%X{tenant_id}','%p')
log4j.appender.DB.layout=org.apache.log4j.PatternLayout

...

id | record_id | value | serverTime
1  |     20    |   0   |  2016-04-19 04:51:16
2  |     20    |   0   |  2016-04-19 04:40:19
3  |     20    |   0   |  2016-04-19 04:27:34
4  |     20    |   70  |  2016-04-19 04:14:24
5  |     20    |   50  |  2016-04-19 04:02:21

输出：

select value from value_record
where record_id in(20) 
order by serverTime desc limit 1;

但预期输出为：

表示如果当前值为零，则查询返回前一行而非零，并显示非零值。

如何在mysql中实现这一点？

Answer 1

您需要过滤不同于0的值，并且您不需要IN子句：

SELECT
    `value`
FROM
    value_record
WHERE
    record_id = 20
    AND `value` > 0
ORDER BY
    serverTime DESC
LIMIT 1;

Answer 2

SELECT value 
FROM value_record 
WHERE record_id IN(20) 
AND value > 0 
ORDER BY serverTime LIMIT 1;

MYSQL - 如果当前值为零，如何获取上一行值

2 个答案: