Basic query: -- Query Information of all employees select * fromemp; -- set the row width setlinesize120; -- set the column width to the width of four digits
Basic query: -- Query Information of all employees select * from emp; -- set the row width set linesize 120; -- set the column width to the width of four digits
Basic query:
Note:
The SQL language is case insensitive.
SQL statements can be written in one or more rows.
Keywords cannot be abbreviated or branch
Each clause is generally written by a branch.
Use indentation to improve statement readability.
Filtering and sorting
Sorting rules:
It can be sorted by the column name in the select statement.
Sort by alias column name
It can be sorted by the sequential values of the column names in the select statement.
If you want to sort by multiple columns, the rule is to first sort by the first column, if the same, then sort by the second column; and so on