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Mampu membuat Tabel di server database (part II)

Mampu membuat Tabel di server database (part II). Mendefinisikan nilai null 1. Apa itu “null” ? “null” tidak dihitung/tidak mempunyai nilai 2. Perbedaan antara nilai “0” dgn “null” “null”  tidak mempunyai nilai sedangkan “0”  mempunyai nilai Contoh buat tabel :

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Mampu membuat Tabel di server database (part II)

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  1. Mampu membuat Tabel di server database (part II) Mendefinisikan nilai null 1. Apa itu “null” ? “null” tidak dihitung/tidak mempunyai nilai 2. Perbedaan antara nilai “0” dgn “null” “null” tidak mempunyai nilai sedangkan “0”  mempunyai nilai Contoh buat tabel : CREATE TABLE datacontoh ( id INT identity,data_A float,data_b float ) Isikan data-datanya ke tabel tersebut : INSERT INTO datacontoh VALUES ( 2, 6) INSERT INTO datacontoh VALUES ( 4, NULL) INSERT INTO datacontoh VALUES ( 5, 0) INSERT INTO datacontoh VALUES ( NULL, 7) Lihat isi datanya dan amati hasilnya : select * from datacontoh1 SELECT id, ( data_a + data_b ) AS jumData FROM datacontoh1 GROUP BY id,data_a,data_b

  2. Mendefinisikan Autonumber • Autonumber  penomoran otomatis Biasa dipakai pada kolom/field yang mengandung Primary Key • Sintak : Fieldname identity (start,increament) • Contoh : CREATE TABLE datacontoh2 ( id int IDENTITY (1, 1) NOT NULL , data_A float NULL , data_b float NULL) ON PRIMARY • Cobalah anda buat tabel dengan cara mengganti start dan increament dari indentity,isikan beberapa buah data, dan lihatlah hasilnya.

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