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From (SQL)
The SQL From clause is the source of a rowset to be operated upon in a Data Manipulation Language (DML) statement. From clauses are very common, and will provide the rowset to be exposed through a Select statement, the source of values in an Update statement, and the target rows to be deleted in a Delete statement. FROM is an SQL reserved word in the SQL standard. The FROM clause is used in conjunction with SQL statements, and takes the following general form: ''SQL-DML-Statement'' FROM ''table_name'' WHERE ''predicate'' The From clause can generally be anything that returns a rowset, a table, view, function, or system-provided information like the Information Schema, which is typically running proprietary commands and returning the information in a table form. Examples The following query returns only those rows from table ''mytable'' where the value in column ''mycol'' is greater than 100. SELECT * FROM mytable WHERE mycol > 100 Requirement The From c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Manipulation Language
A data manipulation language (DML) is a computer programming language used for adding (inserting), deleting, and modifying (updating) data in a database. A DML is often a sublanguage of a broader database language such as SQL, with the DML comprising some of the operators in the language. Read-only selecting of data is sometimes distinguished as being part of a separate data query language (DQL), but it is closely related and sometimes also considered a component of a DML; some operators may perform both selecting (reading) and writing. A popular data manipulation language is that of Structured Query Language (SQL), which is used to retrieve and manipulate data in a relational database.SQL92 Other forms of DML are those used by IMS/DLI, CODASYL databases, such as IDMS and others. SQL In SQL, the data manipulation language comprises the ''SQL-data change'' statements, which modify stored data but not the schema or database objects. Manipulation of persistent database obje ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Select (SQL)
The SQL SELECT statement returns a result set of records, from one or more tables. A SELECT statement retrieves zero or more rows from one or more database tables or database views. In most applications, SELECT is the most commonly used data manipulation language (DML) command. As SQL is a declarative programming language, SELECT queries specify a result set, but do not specify how to calculate it. The database translates the query into a " query plan" which may vary between executions, database versions and database software. This functionality is called the "query optimizer" as it is responsible for finding the best possible execution plan for the query, within applicable constraints. The SELECT statement has many optional clauses: * SELECT clause is the list of columns or SQL expressions that must be returned by the query. This is approximately the relational algebra projection operation. * AS optionally provides an alias for each column or expression in the SELECT c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Update (SQL)
An SQL UPDATE statement changes the data of one or more records in a table. Either all the rows can be updated, or a subset may be chosen using a condition. The UPDATE statement has the following form: :UPDATE ''table_name'' SET ''column_name'' = ''value'' ''column_name'' = ''value ...'' ''WHERE ''condition'' For the UPDATE to be successful, the user must have data manipulation privileges (UPDATE privilege) on the table or column and the updated value must not conflict with all the applicable constraints (such as primary keys, unique indexes, CHECK constraints, and NOT NULL constraints). In some databases, such as PostgreSQL, when a FROM clause is present, what essentially happens is that the target table is joined to the tables mentioned in the fromlist, and each output row of the join represents an update operation for the target table. When using FROM, one should ensure that the join produces at most one output row for each row to be modified. In other words, a target r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delete (SQL)
In the database structured query language ( SQL), the DELETE statement removes one or more records from a table. A subset may be defined for deletion using a condition, otherwise all records are removed. Some database management systems (DBMSs), like MySQL, allow deletion of rows from multiple tables with one DELETE statement (this is sometimes called multi-table DELETE). Examples Delete rows from table ''pies'' where column ''flavor'' equals ''Lemon Meringue'': DELETE FROM pies WHERE flavor='Lemon Meringue'; Delete rows in ''trees'', if the value of ''height'' is smaller than 80. DELETE FROM trees WHERE height < 80; Delete all rows from ''mytable'': [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2003
File:2003 Events Collage.png, From top left, clockwise: The crew of STS-107 perished when the Space Shuttle Columbia Space Shuttle Columbia disaster, disintegrated during reentry into Atmosphere of Earth, Earth's atmosphere; SARS became an 2002–2004 SARS outbreak, epidemic in China, and was a precursor to SARS-CoV-2; A destroyed building in Bam, Iran after the 2003 Bam earthquake killed 30,000 people; A U.S. Army M1 Abrams tank patrols the streets of Baghdad after the city Battle of Baghdad (2003), fell to U.S.-led forces; Abu Ghraib torture and prisoner abuse, Abuse and torture of Iraq, Iraqi prisoners at Abu Ghraib prison by U.S. personnel; Protests against the Iraq War, Protests in London against the 2003 invasion of Iraq, Invasion of Iraq; "Mission Accomplished" became an ironic symbol of the protractedness of the Iraq War after President George W. Bush's infamous Mission Accomplished speech, speech; a statue of Saddam Hussein is toppled in Baghdad after he was deposed during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DUAL Table
The DUAL table is a special one-row, one-column table present by default in Oracle and other database installations. In Oracle, the table has a single VARCHAR2(1) column called DUMMY that has a value of 'X'. It is suitable for use in selecting a pseudo column such as SYSDATE or USER. Example use Oracle's SQL syntax requires the FROM clause but some queries don't require any tables - DUAL can be used in these cases. SELECT 1+1 FROM dual; SELECT 1 FROM dual; SELECT USER FROM dual; SELECT SYSDATE FROM dual; SELECT * FROM dual; History Charles Weiss explains why he created DUAL: I created the DUAL table as an underlying object in the Oracle Data Dictionary. It was never meant to be seen itself, but instead used inside a view that was expected to be queried. The idea was that you could do a JOIN to the DUAL table and create two rows in the result for every one row in your table. Then, by using GROUP BY, the resulting join could be summarized to show the amount of storage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oracle Database
Oracle Database (commonly referred to as Oracle DBMS, Oracle Autonomous Database, or simply as Oracle) is a multi-model database management system produced and marketed by Oracle Corporation. It is a database commonly used for running online transaction processing (OLTP), data warehousing (DW) and mixed (OLTP & DW) database workloads. Oracle Database is available by several service providers on-prem, on-cloud, or as a hybrid cloud installation. It may be run on third party servers as well as on Oracle hardware ( Exadata on-prem, on Oracle Cloud or at Cloud at Customer). History Larry Ellison and his two friends and former co-workers, Bob Miner and Ed Oates, started a consultancy called Software Development Laboratories (SDL) in 1977. SDL developed the original version of the Oracle software. The name ''Oracle'' comes from the code-name of a CIA-funded project Ellison had worked on while formerly employed by Ampex. Releases and versions Oracle products follow a cus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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