MySQL如何在单个查询中执行if是否存在增量 [英] MySQL how to do an if exist increment in a single query

问题描述

我只希望有一个表来按天存储许多事件.

I just wish to have a table to store a number of events by day.

提供表格:

create table totals (
    entryday date,
    total int(11) default 0 not null,
    primary key (entryday) );

如何编写一个递增但创建必需查询的简单查询?

How can I write a simple query which increments, but creates an necessary?

我尝试过-但是它没有增加(它保持为1):

I tried this - but it is not incrementing (it remains at 1):

REPLACE totals SET total = total + 1, entryday = "08-01-11"

显然，这可以很简单地在2个查询中完成，但是它是通过JDBC调用进行的，并且可以被多次调用，因此1个查询会更好.

Obviously this could be done in 2 queries quite simply, but it's through JDBC calls and may be called many times, so 1 query would be better.

推荐答案

您可能想要

You probably want ON DUPLICATE KEY:

INSERT INTO totals (entryday, total)
VALUES ("08-01-11", 1)
ON DUPLICATE KEY UPDATE total = total + 1

如果该日期尚无行，则将"08-01-11" total设置为1，如果total设置为1，则将其递增1.

That'll set the "08-01-11" total to 1 if a row doesn't already exist for that date and increment the total by 1 if it does.

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