Praktikum 6 bab6

Praktikum 6 Basis DataTIPE DATA Praktikum Sistem Basis Data I PostgreSQL 8.X Pertemuan 6 Oleh: Saepudin Nirwan, S.Kom., M.Kom. Purpose of Data Types It is tempting to think that databases would be easier to use if only one data type existed -- a type that could hold any type of information, such as numbers, character strings, or dates. Although a single data type would certainly make table creation simpler, having different data types offers definite advantages: Consistent Results Columns of a uniform type produce consistent results. Displaying, sorting, aggregates, and joins deliver consistent results. No conict arises over how different types are compared or displayed. For example, selecting from an INTEGER...

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Praktikum 5

BAB 5 Example of Aggregates Aggregates can be combined with a WHERE clause to produce more complex results. For example, the query SELECT AVG(age) FROM friend WHERE age >= 21 computes the average age of people age 21 or older. This prevents Dick Gleason from being included in the average computation because he is younger than 21. NULL values are not processed by most aggregates, such as MAX(), SUM(), and AVG(); they are simply ignored. However, if a column contains only NULL values, the result is NULL, not zero. COUNT(*) is different in this respect. Aggregate Function COUNT(*)SUM(colname)MAX(colname)MIN(colname)AVG(colname) Count of rowstotalmaximumminimumaverage...

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CDM PDM perpustakaan

                                                                               CDM perpustakaan   PDM perpustakaan ...

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Penjelasan PostgreSQL

PostgreSQL adalah sebuah perangkat lunak bebas object-relational database server ( database sistem manajemen ), dirilis di bawah fleksibel lisensi BSD-style . It offers an alternative to other open-source database systems (such as MySQL and Firebird ), as well as to proprietary systems such as Oracle , Sybase , IBM's DB2 and Microsoft SQL Server . Ia menawarkan alternatif sumber database terbuka sistem lain (seperti MySQL dan Firebird ), serta kepemilikan sistem seperti Oracle , Sybase , IBM DB2 dan Microsoft SQL Server . PostgreSQL's unusual-looking name gives some readers pause in trying to pronounce it, especially those who pronounce "SQL" as "sequel". PostgreSQL nama tidak biasa tampak memberikan beberapa pembaca jeda dalam mencoba mengucapkannya, terutama mereka yang mengucapkan...

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