Search results
Results from the WOW.Com Content Network
In SQL, the unique keys have a UNIQUE constraint assigned to them in order to prevent duplicates (a duplicate entry is not valid in a unique column). Alternate keys may be used like the primary key when doing a single-table select or when filtering in a where clause, but are not typically used to join multiple tables.
For referential integrity to hold in a relational database, any column in a base table that is declared a foreign key can only contain either null values or values from a parent table's primary key or a candidate key. [2] In other words, when a foreign key value is used it must reference a valid, existing primary key in the parent table.
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.
Computer programming or coding is the composition of sequences of instructions, called programs, that computers can follow to perform tasks. [1] [2] It involves designing and implementing algorithms, step-by-step specifications of procedures, by writing code in one or more programming languages.
The central concept of a document-oriented database is the notion of a document.While each document-oriented database implementation differs on the details of this definition, in general, they all assume documents encapsulate and encode data (or information) in some standard format or encoding.
The provision of a unique append-write mode (MDB_APPEND) [1] is implemented by allowing the new record to be added directly to the end of the B+ tree. This reduces the number of reads and writes page operations, resulting in greatly-increased performance but requiring the programmer to ensure keys are already in sorted order when storing in the DB.
Arguments are given after the command, and are separated from the command using a space. [11] For example, the command to set the trigger mode of an instrument to "normal" may be given as "TRIGger:MODe NORMal". Here, the word "NORMal" is used as the argument to the "TRIGger:MODe" command. When multiple arguments are provided, the arguments are ...
The concept is similar to system identification in the model predictive control domain but it is working with fuzzy models instead of differential equations. The numerical values of the input/output set are clustered and transformed into fuzzy predicates. [14] Fuzzy q-learning A model free learning algorithm to control complex systems. The ...