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A Primary Key is a set of attributes that uniquely identifies items in a DynamoDB Table. Creation of a DynamoDB Table requires definition of a Primary Key. Each item in a DynamoDB Table is required to have all of the attributes that constitute the Primary Key, and no two items in a Table can have the same Primary Key.
With the same table, the query SELECT C1 FROM T will result in the elements from the column C1 of all the rows of the table being shown. This is similar to a projection in relational algebra , except that in the general case, the result may contain duplicate rows.
The following example of a SELECT query returns a list of expensive books. The query retrieves all rows from the Book table in which the price column contains a value greater than 100.00. The result is sorted in ascending order by title. The asterisk (*) in the select list indicates that all columns of the Book table should be included in the ...
An SQL injection takes advantage of SQL syntax to inject malicious commands that can read or modify a database or compromise the meaning of the original query. [13] For example, consider a web page that has two text fields which allow users to enter a username and a password.
Oracle Big Data SQL is a common SQL access layer to data stored in Hadoop, HDFS, Hive and OND. This allows customers to query Oracle NoSQL Data from Hive or Oracle Database. Users can run MapReduce jobs against data stored in OND that is configured for secure access. The latest release also supports both primitive and complex data types
Major DBMSs, including SQLite, [5] MySQL, [6] Oracle, [7] IBM Db2, [8] Microsoft SQL Server [9] and PostgreSQL [10] support prepared statements. Prepared statements are normally executed through a non-SQL binary protocol for efficiency and protection from SQL injection, but with some DBMSs such as MySQL prepared statements are also available using a SQL syntax for debugging purposes.
A common table expression, or CTE, (in SQL) is a temporary named result set, derived from a simple query and defined within the execution scope of a SELECT, INSERT, UPDATE, or DELETE statement. CTEs can be thought of as alternatives to derived tables ( subquery ), views , and inline user-defined functions.
This would allow any customer to be serviced without waiting for another customer who is accessing a different account. This is analogous to a record level lock and is normally the highest degree of locking granularity in a database management system. In a SQL database, a record is typically called a "row".