Is this my understanding of the order by of the sql statement correct?? Rookie Question .

1.It's interesting to understand, but the reality should be: if there are more than two fields after order by, then all the records in the result set are sorted by the previous field, and the same part of the previous field is sorted by the next field. For example:

order by Gender Age Name.

The sort result is.

Male 20 Anyi.

Male 20 Zhang San.

Male 30 An Xiaoyi.

Female 18 Lin Wen.

Female 18 Wei Feng.

2.That's right. 3.The result you said is correct, but it's not that "there will always be a default order by id asc", it's that if you don't write order by, the result set will be output in the order in which the data records were physically written.

4.You can achieve the effect you want.

It doesn't have to be that complicated, just remember one thing :

order by a,b

Sort by a first, then by b if the order of a is the same.

As for whether it is in ascending order or descending order, (asc and desc are not written by default, asc), writing desc is descending.

It's as simple as that, and if you think about it too much, it's troublesome.

Above, I hope it will help you.

The understanding is correct, but the formulation is somewhat cumbersome.

Order by is parsed in left-to-right order, and the default is ASC (non-descending).

from,where parses from right to left, so the fewer table records on the far right, the better, and the more accurate the conditions on the right, the better.

For example: select .from tb1,tb2 where f1>1000 and f2='samsung'

tb1 has 10000 records, tb2 has 100 records, f2='samsung'More accurate than f1>1000.

Order pretty much does what it means.

The top field should be a bit: default 0, top 1, not top 0

select ..from ..order by top desc, last modified desc

If you sort by ID, then the replies are useless.

The landlord has quick thinking and clear thinking, and he has written an encyclopedia for order by use, which is very correct.

Pretty much correct.

However, the top part should be set to the top field as bit.

Then order by top

Why doubt yourself? Your understanding is absolutely correct!

Order by id desc does not write desc, which means ascasc is the default sort.

If you use the Zhenxu Jingde statement to query in sqlsever, change the equal sign after where to zhi to *=i.e., left join).

One of the more confusing points is that count() is used to count the number of tuples, order by is followed by count() to count the numerical value, and order by is used to sort the query results in ascending order (asc) or descending order (desc) of one or more attribute columns. Note that the attribute column is sorted, not a specific value of caution.

Order by id desc does not write desc, which means ascasc is the default sort.

If you use that statement in sqlsever, change the equal sign after where to *= (i.e., left join).

One of the more confusing points is that count() is used to count the number of tuples, order by is followed by count(), and order by is used to sort the query results in ascending order (asc) or descending order (desc) of one or more attribute columns. Note that the attribute column is sorted, not a specific numeric value.

order by @id should not be wrong, the default is in ascending order, unless you have a problem with your @id variable and want to have multiple order by, order by @id , order by @name desc

I'm not going to say anything, just give you an example, no matter how much I say, there are no examples that are useful.

select name,count(*)numberfrom users

group by name

order by 2 desc

Query the number of people with the same name in the users table, and sort them according to the number of names with the most duplicate names.

Group by first

Then order by

Order by should always be executed last.

group by is grouping, order by is sorting, first group by and then order by

Use group by first, then order by, and order by is always last.

The order by statement is used forAccording to the specified columnsRightResult setConductedSorting

order by statementDefaultIn accordance withAscendingSort the records.

If you wish to follow theDescendingYou can use it to sort recordsdescKeywords.

Note: When sorting strings, pressThe first characterofASCII valuearrangement, if the first character is the same, look backward one bit.

The original table (used in the example):

orders table:

Example 1 displays the company name in alphabetical order:

select company, ordernumber from orders order by company

Example 2 displays the company name in alphabetical order and the ordernumber in numerical order

select company, ordernumber from orders order by company, ordernumber

Example 3 displays the company name in reverse alphabetical order:

select company, ordernumber from orders order by company desc

Result: Instance 4

The company name is displayed in reverse alphabetical order and the sequence number is displayed in numerical order:

select company, ordernumber from orders order by company desc, ordernumber asc

Results: Note: There are two equal company names (w3school) in the results above.

Only this time, when there is the same value in the first column, the second column is in ascending order. This is also the case if some of the values in the first column are nulls.

Problem description

If the field used in mysql sorting is character, it will be sorted out like this:

This sort is compared by character starting with the first character, but not what we want, what we want is:

Solution

When sorting, convert the corresponding fields to integers and use the cast function, as follows:

cast(seat_row as unsigned)

Convert the seat row column to an unsigned numeric type.