22538477
Description
Mind Map by Nathaniel Burke, updated more than 1 year ago
More
Structured Query
Language (SQL)
- "SELECT" and "WHERE" Clauses
- I think the project would be a
good fit for an EPQ as it would be
a large project and I could do a lot
of evaluation on aspects such as
performance on different
computers and alternate
solutions with different
advantages and disadvantages.
- These tables are made up of rows
(records) and columns (attributes).
Each piece of data representing a
values for a specific record for a
specific attribute is called a field.
- These tables are made up of rows
(records) and columns (attributes).
Each piece of data representing a
values for a specific record for a
specific attribute is called a field.
- Each "entity" in a database is known as a record and
has multiple fields which hold data about the record.
- Records in one table are able to refer to
records in another table using "foreign
keys" that represent the primary keys of
records in that table that the record is
related to.
- Records are distinguished from one
another by each having a unique
primary key which will be contained
in the first column of the table for
the records.
- Sometimes, giving each record a unique primary
key in a database is not possible or easy. In this
case, multiple keys can be combined to create a
composite key that acts as the primary key.
- Sometimes, giving each record a unique primary
key in a database is not possible or easy. In this
case, multiple keys can be combined to create a
composite key that acts as the primary key.
- Records in one table are able to refer to
records in another table using "foreign
keys" that represent the primary keys of
records in that table that the record is
related to.
- Databases with only one table are
known as flat-file databases. These are
very inefficient.
- The process of converting from
a flat-file database to a
relational database is known
as "normalisation".
- The process of converting from
a flat-file database to a
relational database is known
as "normalisation".
- Databases with multiple
tables with links
between them are
known as relational
databases.
- I think the project would be a
good fit for an EPQ as it would be
a large project and I could do a lot
of evaluation on aspects such as
performance on different
computers and alternate
solutions with different
advantages and disadvantages.
- Syntax
- The syntax of SQL is is very
logical and close to English,
making it intuitive to
understand.
- SQL commands can be broken up
into clauses/statements and
predicates and expressions.
- For example, in the command "SELECT * FROM
People WHERE Name = ‘John’", both "SELECT * FROM
People" and "WHERE Name='John'" are
clauses/statements, "Name='John'" is a predicate and
"'John'" is an expression.
- For example, in the command "SELECT * FROM
People WHERE Name = ‘John’", both "SELECT * FROM
People" and "WHERE Name='John'" are
clauses/statements, "Name='John'" is a predicate and
"'John'" is an expression.
- SQL commands can be broken up
into clauses/statements and
predicates and expressions.
- The syntax of SQL is is very
logical and close to English,
making it intuitive to
understand.
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