SQL (STRUCTURED QUERY LANGUAGE)

DML

Bahasa untuk mengakses basis data Bahasa untuk mengolah basis data Bahasa untuk memanggil fungsi-fungsi

agregasi Bahasa untuk melakukan query Jenis-jenis query:

Sederhana Join Bertingkat

CONTOH PENGGUNAAN SKEMA

SQL is based on set and relational operations with certain modifications and enhancements

A typical SQL query has the form:select A1, A2, ..., Anfrom r1, r2, ..., rmwhere P

Ais represent attributes ris represent relations P is a predicate.

This query is equivalent to the relational algebra expression.

ÕA1, A2, ..., An(sP (r1 x r2 x ... x rm)) The result of an SQL query is a relation.

QUERY SEDERHANA

Bentuk umum SQL:SELECT [ALL|DISTINCT]

nama_kolom_kolom_tabel[INTO nama_tabel][FROM nama_nama_tabel][WHERE predikat][GROUP BY ekspresi][ORDER BY nama+kolom_tabel]

The select clause corresponds to the projection operation of the relational algebra. It is used to list the attributes desired in the result of a query.

Find the names of all branches in the loan relationselect branch-namefrom loan

In the “pure” relational algebra syntax, the query would be:Õbranch-name(loan)

An asterisk in the select clause denotes “all attributes”select *from loan

NOTE: SQL does not permit the ‘-’ character in names, so you would use, forexample, branch_name instead of branch-name in a real implementation. We use ‘-’ since it looks nicer!

NOTE: SQL names are case insensitive, meaning you can use upper case or lower case.You may wish to use upper case in places where we use bold font

SQL allows duplicates in relations as well as in query results. To force the elimination of duplicates (menghilangkan

duplikasi penampilan output yang sama) insert the keyword distinct after

select. Find the names of all branches in the loan relations, and remove duplicates select distinct branch-name from loan

The keyword all specifies that duplicates not be removed. select all branch-name from loan

Menampilkan isi tabel customer select * from customer

Menampilkan semua fname dari tabel customer select customer_name from customer

Menampilkan account number dan balance dari kantor cabang (branch_name) “Pondok Kelapa”

select account_number, balancefrom accountwhere branch_name = “Pondok Kelapa”;

Perintah diatas dapat juga dituliskan dengan menggunakan qualified column names sebagai berikut:

select account.account_number,account.balancefrom accountwhere branch_name = “Pondok Kelapa”;

The select clause can contain arithmetic expressions involving the operation, +, –, *, and /, and operating on constants or attributes of tuples.

The query:select loan-number, branch-name, amount * 100from loan

would return a relation which is the same as the loan

would return a relation which is the same as the loan relations, except

that the attribute amount is multiplied by 100.