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Technical Articles

Database

SQL

Usage of rank in sql

The RANK function in SQL ranks rows according to the specified column. The result set returns the ranking of each row, starting from 1, and the same value has the same ranking. The partition expression can specify the partition column, ranking is only performed within each partition, the sort expression specifies the sort column, and the ranking is determined according to the order of the data in this column.

May 02, 2024 am 02:30 AM

聚合函数

How to use rank function in sql

The RANK() function in SQL is used to rank rows in a query result set, assigning a ranking value that represents each row's relative position in a group or table. Usage: RANK() OVER ([PARTITION BY grouping field] ORDER BY sorting field). Parameters: PARTITION BY grouping field (optional): Group the result set and rank each group separately. ORDER BY sorting field: the column to rank by. Return value: An integer representing the relative ranking of the row.

May 02, 2024 am 02:27 AM

How to use round in sql

The SQL ROUND function is used to round a number to a positive number of digits to the right of the decimal point and a negative number to the left of the decimal point. When used, specify the number and digits to be rounded. For example, ROUND(123.456, 2) will round to two digits to the right of the decimal point, and the result is 123.46.

May 02, 2024 am 02:24 AM

How to descend in sql

In SQL, sort in descending order using the ORDER BY clause, whose syntax is ORDER BY <column name> DESC. Multiple columns can be sorted in descending order and added to the clause in the order of column names, such as ORDER BY <column name 1> DESC, <column name 2> DESC.

May 02, 2024 am 02:18 AM

How to write like statement in sql

The LIKE statement in SQL is used to match strings based on a pattern, using the % and _ wildcard characters to match zero or more characters and a single character respectively. The syntax of the LIKE statement is: SELECT * FROM table_name WHERE column_name LIKE 'pattern'.

May 02, 2024 am 02:15 AM

What do ANY and ALL mean in sql?

In SQL, ANY and ALL are used to handle grouping conditions: ANY checks whether any row in the group satisfies the condition, while ALL checks whether all rows in the group satisfy the condition.

May 02, 2024 am 02:03 AM

How to use filename in sql

The FILENAME function returns the full path and name of the file system. It can be used with the following syntax: SELECT FILENAME(<file_name>). This function allows you to access data stored in the file system by specifying the file path in OPEN and EXECUTE statements.

May 02, 2024 am 02:00 AM

What can be used to replace in in sql

The OR operator can be used as an alternative to the IN operator in SQL to efficiently check whether a value is contained in a specified list. The advantage of the OR operator is that its syntax is intuitive and easy to use, especially when there are many list values. It is important to note that the OR operator can only be used to compare a single column and must be used with caution when including NULL in the list, because NULL is not equal to any other value.

May 02, 2024 am 01:57 AM

What does using mean in sql

In SQL, USING is used to specify the connection relationship between two tables, simplifying queries and improving performance. It is used as follows: 1. Determine the joining column. 2. Use the USING clause to specify the join columns. 3. Specify the table name to be connected.

May 02, 2024 am 01:45 AM

What does dbms mean in sql

DBMS is the key system in SQL that manages databases and is responsible for storing data, controlling access, maintaining integrity, optimizing performance, and providing backup and recovery. Types include relational DBMS, non-relational DBMS, and cloud databases. DBMS is crucial in SQL as it provides the framework for the management and control of the database and its data.

May 02, 2024 am 01:42 AM

数据访问键值对

What does dba mean in sql

A DBA in SQL is a database administrator who is responsible for the management and maintenance of the database, including: Database design and implementation Performance optimization Backup and recovery Security management Change management User support

May 02, 2024 am 01:39 AM

数据访问数据丢失

What does use mean in mysql

The USE command in MySQL is used to switch to a specified database, making the contents of that database available to subsequent queries.

May 02, 2024 am 01:36 AM

mysql

statement to delete column in sql

In SQL, the syntax to delete a table column using the ALTER TABLE statement is: ALTER TABLE table_name DROP COLUMN column_name. This statement permanently deletes all data in the specified column. If the column is part of a foreign key, unique constraint, or primary key, the associated constraints must also be deleted.

May 02, 2024 am 01:33 AM

How to use minus in sql

The MINUS operator in SQL is used to subtract rows from one table in another table and return the difference between the two sets of rows: Syntax: SELECT FROM table1 MINUS SELECT FROM table2 Difference and EXCEPT: The MINUS operator will eliminate duplicates OK, EXCEPT does not.

May 02, 2024 am 01:30 AM