Null (SQL)

Null (SQL), Marker used in SQL databases to indicate a value does not exist.

Null (SQL) image

Null or NULL is a special marker used in Structured Query Language to indicate that a data value does not exist in the database. Introduced by the creator of the relational database model, E. F. Codd, SQL Null serves to fulfil the requirement that all true relational database management systems (RDMS) support a representation of "missing information and inapplicable information". Codd also introduced the use of the lowercase Greek omega (ω) symbol to represent Null in database theory. In SQL, NULL is a reserved word used to identify this marker. A null should not be confused with a value of 0.

Join (SQL)
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Join (SQL) ... department. This is the SQL statement to create the above tables: CREATE TABLE department( DepartmentID INT PRIMARY KEY NOT NULL, DepartmentName VARCHAR(20)...

5 months ago

Null ... Null may refer to: Null (SQL) (or NULL), a special marker and keyword in SQL indicating that something has no value Null character, the zero-valued ASCII...

SQL syntax
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SQL syntax ... anything with Null directly, SQL provides two Null-specific comparison predicates: IS NULL and IS NOT NULL test whether data is or is not Null. SQL does not...

SQL injection
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SQL injection ... SQL injection is a code injection technique used to attack data-driven applications, in which malicious SQL statements are inserted into an entry field...

Null symbol
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Null symbol ... Null symbol may refer to: Null character, U+0000, U+2400 "symbol for null" (␀), a single-character glyph "NUL" Null sign (∅), the empty set Null (SQL)...

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SQL ... SQL (/ˌɛsˌkjuːˈɛl/ (listen) S-Q-L, /ˈsiːkwəl/ "sequel"; Structured Query Language) is a domain-specific language used in programming and designed for...

2 months ago

PL/SQL ... PL/SQL (Procedural Language for SQL) is Oracle Corporation's procedural extension for SQL and the Oracle relational database. PL/SQL is available in Oracle...

Data definition language
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Data definition language ... In the context of SQL, data definition or data description language (DDL) is a syntax for creating and modifying database objects such as tables, indices...

Microsoft SQL Server
4 months ago

Microsoft SQL Server ... Microsoft SQL Server is a relational database management system developed by Microsoft. As a database server, it is a software product with the primary...

Null coalescing operator
5 months ago

Null coalescing operator ... defined to be NULL or not. The ANSI SQL-92 standard includes the COALESCE function implemented in Oracle, SQL Server, PostgreSQL, SQLite and MySQL. The COALESCE...

Nullable type
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Set operations (SQL)
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Where (SQL)
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Insert (SQL)
1 month ago
Entity integrity
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Update (SQL)
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Foreign key
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Boolean data type
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