Mysql query, data shows the empty set-CodePudding

There is a data table, there are more than 1800 ten thousand data, table structure is as follows:

Check out the following:

Why the second query result is empty, mystery, hope bosses give directions, thank you.

CodePudding user response:

Limit the number after the representative from article 10000000 data reverse output to article 8, you only have 7, article 8 to article 10000000 data is Empty, Empty set of course

CodePudding user response:

reference 1st floor weixin_43568294 response:

limit at the back of the Numbers represent article 10000000 data from the output to article 8 in reverse chronological order, you only have 7, article 8 to article 10000000 data is Empty, Empty set of course

Please comment:
Limit N, M not from the meaning of article N, M output records?
You said the reverse order of the output to article 8 a little look not to understand?

CodePudding user response:

Guess the Mysql will be your first query results as a cache, for your second query, so you only 7 second query data, the result is the empty set

CodePudding user response:

 the explain the select * from card limit, 10000000, 7; 
Explain the select card_id from card limit 10000000, 7;

Look at the execution plan

CodePudding user response:

The first statement, 2 consecutive times, what the result will be,

CodePudding user response:

refer to the second floor daily necessities sauce vinegar 0 reply:

Quote: refer to 1st floor weixin_43568294 response:

Limit the number after the representative from article 10000000 data reverse output to article 8, you only have 7 data, article 8 to article 10000000 data is Empty, Empty set of course

Please comment:
Limit N, M not from the meaning of article N, M output records?
You said the reverse order of the output to article 8 a little look not to understand?

I understand is wrong, what you said is accurate. The output since 100000000 7, but only seven data, so it is the Empty set