sql tutorial oracle

SQL Tutorial: Oracle

Oracle is one of the most widely used and popular database management systems in the industry. Oracle Corporation is one of the most influential software companies in the world and a leader in data management software. Oracle's database system has become a very important infrastructure in almost all enterprises. This article will introduce the basic syntax of Oracle SQL and some commonly used operations.

Oracle SQL basic syntax

SQL is the full name of Structured Query Language, which is a language used to manage data storage and retrieval. In the Oracle database, SQL is the language that performs operations such as queries, inserts, updates, and deletes. Here is some basic SQL syntax:

1. SELECT statement

The SELECT statement is used to retrieve data from a table. The following is the syntax of a basic SELECT statement:

SELECT column1, column2, ...columnN FROM table_name;

Among them, column1, column2, ...columnN represents the data columns to be retrieved , table_name represents the name of the table to be retrieved.

For example, to retrieve data for the "customer_name" and "customer_id" columns in a table named "customers", you can use the following statement:

SELECT customer_name, customer_id FROM customers;

2. WHERE statement

The WHERE statement is used to filter data in the table. It can select qualified data rows based on one or more conditions. The following is the basic syntax of a WHERE statement:

SELECT column1, column2, ...columnN FROM table_name WHERE [condition];

In the condition, you can use various logical operators, For example, the equal sign "=", the less than sign "<", the greater than sign ">", and logical operators like AND, OR, NOT, etc. are used to filter data rows that meet the conditions.

For example, in a table named "employees", if you only want those records with a "salary" column value greater than 10000, you can use the following statement:

SELECT * FROM employees WHERE salary > 10000;

3. ORDER BY statement

The ORDER BY statement is used to arrange the results in ascending or descending order. The following is the basic syntax of an ORDER BY statement:

SELECT column1, column2, ...columnN FROM table_name ORDER BY column_name [ASC|DESC];

In the ORDER BY clause, you You need to specify a column (or columns) that will be used to sort the results in the specified way (ascending or descending order).

For example, in a table named "customers", if you want to sort by the "customer_name" column in ascending order, you can use the following statement:

SELECT customer_name, city, state FROM customers ORDER BY customer_name ASC;

Common operations

1. Create table

Oracle SQL is a relational database and can define relational tables in the database. The following is a basic syntax for creating a table in Oracle:

CREATE TABLE table_name (
column1 datatype,
column2 datatype,
column3 datatype,
....
columnn datatype
);

For example, to create a table named "employees" containing the fields "employee_name", "employee_id", and "department", you can use the following statement:

CREATE TABLE employees (
employee_name VARCHAR(255),
employee_id INT(10),
department VARCHAR(255)
);

2. Insert data

To insert data into the table, you can use the INSERT INTO statement. The following is the basic syntax of an INSERT INTO statement:

INSERT INTO table_name (column1, column2, column3, ..., columnN) VALUES (value1, value2, value3, ..., valueN);

For example, to insert a record in the "employees" table, you can use the following statement:

INSERT INTO employees (employee_id, employee_name, department) VALUES (1, 'Tom', 'IT');

3. Update data

To update the data in the table, you can use the UPDATE statement. The following is the basic syntax of an UPDATE statement:

UPDATE table_name SET column1 = value1, column2 = value2, ...columnN=valueN WHERE [condition];

For example, in the "employees" table To update the data of the record where "employee_id" is 1, you can use the following statement:

UPDATE employees SET employee_name = 'John' WHERE employee_id = 1;

4. Delete data

To delete data in the table, you can use the DELETE statement. The following is the basic syntax of a DELETE statement:

DELETE FROM table_name WHERE [condition];

For example, to delete the record with "employee_id" 1 in the "employees" table, you can use the following statement ：

DELETE FROM employees WHERE employee_id = 1;

Summary

Oracle SQL is a powerful database management language that can perform data retrieval, insertion, and Operations such as update and delete. This article introduces the basic syntax and common operations of Oracle SQL, which has certain reference value. However, Oracle SQL is a very large subject and only in-depth study can unlock its full potential.

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