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SQL is a well known query language and data manipulation language for relational databases; XQuery is a query language for XML data sources; XPath is a declarative language for navigating XML documents; YQL is an SQL-like query language created by Yahoo! Search engine query languages, e.g., as used by Google [5] or Bing [6]
The SQL function EXTRACT can be used for extracting a single field (seconds, for instance) of a datetime or interval value. The current system date / time of the database server can be called by using functions like CURRENT_DATE , CURRENT_TIMESTAMP , LOCALTIME , or LOCALTIMESTAMP .
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
SQL includes operators and functions for calculating values on stored values. SQL allows the use of expressions in the select list to project data, as in the following example, which returns a list of books that cost more than 100.00 with an additional sales_tax column containing a sales tax figure calculated at 6% of the price.
MySQL (/ ˌ m aɪ ˌ ɛ s ˌ k juː ˈ ɛ l /) [6] is an open-source relational database management system (RDBMS). [6] [7] Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, [1] and "SQL", the acronym for Structured Query Language.
Drilling Formula Sheets is a set of Drilling Formulas used commonly by drilling engineers in the onshore and offshore oil drilling industry. They are used as part of a key piece of engineering work called Well Control .
There is no DATETIME type. And there is a TIME type. But there is no TIMESTAMP type that can contain fine-grained timestamp up to millisecond or nanosecond. The TO_DATE function can be used to convert strings to date values. The function converts the first quoted string into a date, using as a definition the second quoted string, for example:
A WHERE clause in SQL specifies that a SQL Data Manipulation Language (DML) statement should only affect rows that meet specified criteria. The criteria are expressed in the form of predicates. WHERE clauses are not mandatory clauses of SQL DML statements, but can be used to limit the number of rows affected by a SQL DML statement or returned ...