Structured Query Language (SQL) is the
set of statements with which all programs and users access data in an Oracle
database.
ER diagrams
Voorbeelden!!! Plaatje!
What can SQL do for you?
What can you do with SQL?
Overzicht van atomaire datatypen
BYTE indicates that the column will have
byte length semantics; CHAR indicates that the column will have character
semantics.
Arithmetical expressions with NULL values return NULL.
The NVL function NVL( x, 0 ) returns 0 is x is NULL, else it returns x.
DDL – Data Definition Language – CREATE/DROP
DML – Data Modification Language INSERT/UPDATE
Lay-out is free format
Layout is free format
How to use numerical constant and character constants (delimited by single quotes)
Layout is free format
How to use numerical constant and character constants (delimited by single quotes)
NULL
is substituted for the missing ra, dec, bmag VALUES in the second example
De WHERE clause moet worden uitgelegd
VOOR de DELETE/UPDATE en JOIN
Expressions are allowed in the selection clause and in the where
clause
Use of aliasses!
_ is the wildcard for a single character
% is the wildcard for zero or more characters
The SET clause allows the use of
expressions for each attribute
Only joins rows for which name does not contain the NULL value!!!
FROM a, b means the cartesian product of a and b (m rows in a, n rows in b means
m*n rows for the cartesian product!)