COMP9311 Database Systems WEEK8

1. Database Programming

在Procedural Language中操作数据库时，往往包含三个步骤：
（1）code in a programming language（PHP比较常用）
（2）SQL query/update statments（用来获得数据库的信息）
（3）code to map between tuples and PL data（连接PL和database）
从网页调取数据的时候，除了sql, PHP外，往往还需要用到html, css和javascript。

2. Catalogs

Catalogs是关于databse的数据，比如有多少table，多少trigger，多少fuction等。system catalog也被叫做data dictionary或者system view。
SQL:2003 standard metadata: INFORMATION_SCHEMA.
INFORMATION_SCHEMA is available globally and includes:
--Schemata(catalog_name, schema_name, schema_owner, ...)
--Tables(table_catalog, table_schema, table_name, table_type, ...)
--Columns(table_catalog, table_schema, table_name, column_name, ordinal_position, column_default, data_type, ...)
--Views(table_catalog, table_schema, table_name, view_definition, ...) Table_Constraints(..., constraint_name, ..., constraint_type, ...)

2.1 练习1

访问Catalog获取databse的table信息：

create or replace view myTables
as
select table_name
from   information_schema.tables
where  table_schema = 'public' and table_type = 'BASE TABLE'
order  by table_name;

2.2 练习2

访问Catalog获取table和attributes信息：

create or replace view myTableColumns
as
select t.table_name, c.column_name
from   information_schema.tables t
    join information_schema.columns c
    on (t.table_name = c.table_name)
where  t.table_schema = 'public' and t.table_type = 'BASE TABLE'
order  by t.table_name, c.ordinal_position;

create or replace view mySchema("table","attributes")
as
select table_name, concat(column_name)
from   myTableColumns
group  by table_name
order  by table_name;

2.3 练习3

写一个plpgsql函数实现以下功能：
--whose argument is a table name (from the public schema)
--whose result is a CREATE TABLE statement to build the table
--only handle constraints mentioned in the columns table

create type ColumnRecord as (
    "table" text,
    "column" text,
    "type" text,
    "constraint" text
);

create or replace function
    colDataType(_col information_schema.columns) returns text
as $$
declare
    _out text;
begin
    _out := _col.data_type;
    _out := _out||coalesce(' '||_col.character_maximum_length::text,'');
    -- if (_col.character_maximum_length is not null) then
    --    _out = _out||(_col.character_maximum_length::text);
    -- end if;
    _out := replace(_out,'character varying','varchar');
    if (_out like 'timestamp%') then _out := 'timestamp'; end if;
    return _out;
end;
$$ language plpgsql;

create or replace function
    colConstraints(_col information_schema.columns) returns text
as $$
declare
    _rec record;
    _out text;
begin
    _out := '';
    if (_col.is_nullable = 'NO') then
        _out := _out||','||'NOT NULL';
    end if;
    for _rec in
        select tc.constraint_type
        from   information_schema.constraint_column_usage ccu
            join information_schema.table_constraints tc
                on (ccu.constraint_name = tc.constraint_name)
        where  tc.table_name = _col.table_name
            and ccu.column_name = _col.column_name
    loop
        _out := _out||','||_rec.constraint_type;
    end loop;
    return substring(_out,2,length(_out));
end;
$$ language plpgsql;

create or replace function
    schema() returns setof ColumnRecord
as $$
declare
    _col information_schema.columns;
    _c ColumnRecord;
begin
    for _col in
        select c.*
        from information_schema.tables t
            join information_schema.columns c
            on (t.table_name = c.table_name)
        where t.table_schema='public' and t.table_type = 'BASE TABLE'
    loop
        _c."table"      := _col.table_name;
        _c."column"     := _col.column_name;
        _c."type"       := colDataType(_col);
        _c."constraint" := colConstraints(_col);
        return next _c;
    end loop;
    return;
end;
$$ language plpgsql;

3. Security, Privilege, Authorisation

3.1 Access Control

创建用户：

CREATE USER Name IDENTIFIED BY 'Password'
ALTER USER Name IDENTIFIED BY 'NewPassword'
ALTER USER Name WITH Capabilities
ALTER USER Name SET ConfigParameter = ...

创建用户分组：

CREATE GROUP Name
ALTER GROUP Name ADD USER User1, User2, ...
ALTER GROUP Name DROP USER User1, User2, ...

设置用户权限：

CREATE ROLE UserName Options
-- where Options include ...
PASSWORD 'Password'
CREATEDB | NOCREATEDB
CREATEUSER | NOCREATEUSER
IN GROUP GroupName
VALID UNTIL 'TimeStamp'