Introduction to mysql operation (4) ----- data sorting (ascending, descending, multi-field sorting)

The content of the emp table is known as

1.Ascending

Syntax: select field name 1, field name 2, field name 3 from table name (where condition) order by (field);

Example: Sort salary in ascending order

You can also sort strings in ascending order, the order is according to the first letter, from a-z:

The default ordering of order by is ascending order. You can also add asc after order by (field) to indicate ascending order, and the effect is the same as the default.

2. Descending data order

Syntax: select field name 1, field name 2, field name 3 from table name (where condition) order by (field) desc;

Sort employees' salaries in descending order: (In ascending order by name when salaries are the same)

3. Sorting by multiple fields

When we sort in ascending order above, we found that when the salary is the same, the name ename is not sorted in ascending order.

Example: Arrange in ascending order of salary, and arrange in ascending order of name when the salary is the same.

Note: order by (field one) (ascending/descending), (field two) (ascending/descending), (field n) (ascending/descending)…

The field next to the order by plays a leading role together. When the first field in front cannot be judged, the second field in the back, field n, is used.

Sort by field index selected to find:

For example: select job,ename,sal from emp order by 1; //1 means the first field to be searched, that is, job, then the following is arranged in ascending order of jobs.If it is 2, it will be sorted in ascending order of ename.3 is sal..Anyway, this index is related to the position of the field you choose to find.

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Simple exercise: Find out the employees whose jobs are SALESMAN in the emp table and sort them in descending order of salary.

sql statement: select ename,job,sal from emp where job='SALESMAN' order by sal desc;

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