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Introduction

IT Notes → Database → Oracle @ December 22, 2020

GENERAL:

  • SQL is 4GL.
  • “” can be used to make case sensitive for column names.
  • Schema is like a folder in a database. It is objects that can be owned by a user account.

NORMAL FORM:

  • 1NF –> No repeating groups 2-dimensional.
  • 2NF –> Primary key that is not composite.
  • 3NF –> No data that does not provide the intend of primary key.
  • Boyce-Codd NF –> Remove certain rare logical inconsistencies.
  • 4NF –> Every multivalued dependency is dependent on a super key.
  • 5NF –> Every join dependency is a result of the candidate keys.

NAMESPACE:

  • USER, ROLES, PUBLIC SYNONYMNS System.
  • TABLE, VIEW, SEQUENCE, PRIVATE SYNONYMNS, USER DEFINED TYPES Schema.
  • INDEX Schema.
  • CONSTRAINT Schema.

DATATYPES:

  • CHAR(n) Retrieved with spaces.
  • VARCHAR2(n).
  • NUMBER(n, m) n is precision – total number in either side after scaling m is scale – total number on right side of decimal point. If a value has more significant digits to the left of the decimal place than are specified in the format, then pound signs (#) replace the value. If a positive value is extremely large and cannot be represented in the specified format, then the infinity sign (~) replaces the value. Likewise, if a negative value is extremely small and cannot be represented by the specified format, then the negative infinity sign replaces the value (-~).
  • DATE NLS_DATE_FORMAT NLS_TERRITORY.
  • TIMESTAMP(n 1-9/6).
  • TIMESTAMP(n 1-9/6) WITH TIMEZONE.
  • TIMESTAMP(n 1-9/6) WITH LOCAL TIMEZONE.
  • INTERVAL YEAR(n 1-9/2) TO MONTH.
  • INTERVAL DAY(n1 1-9/2) TO SECOND(n2 1-9/6).
  • BLOB.
  • CLOB.
  • NCLOB (UTF).
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