Understand the similarities and differences in SQL operations between Oracle and DB2

Oracle and DB2 are two common relational database management systems. They both support SQL (Structured Query Language) for database operation and management. Although they both follow the SQL standard, there are some differences in some aspects. This article will focus on the similarities and differences between Oracle and DB2 in SQL operations, and provide specific code examples for readers to better understand.

1. Create a table:

In Oracle, you can use the following SQL statement to create a table named "employee":

CREATE TABLE employee (
    emp_id NUMBER PRIMARY KEY,
    emp_name VARCHAR2(50),
    emp_salary NUMBER
);

In DB2, create a The SQL statement of the table named "employee" is as follows:

CREATE TABLE employee (
    emp_id INTEGER PRIMARY KEY,
    emp_name VARCHAR(50),
    emp_salary DECIMAL(10,2)
);

As you can see, the data types used in Oracle are "NUMBER" and "VARCHAR2", while in DB2 they are "INTEGER" and "VARCHAR" respectively. ” and “DECIMAL”.

2. Insert data:

To insert data in Oracle, you can use the following SQL statement:

INSERT INTO employee(emp_id, emp_name, emp_salary) VALUES (101, 'Alice', 5000);

In DB2, the SQL statement for the same operation is as follows:

INSERT INTO employee(emp_id, emp_name, emp_salary) VALUES (101, 'Alice', 5000.00);

In DB2, you need to pay attention to the precision of decimals, and you need to specify the total length and number of decimal points after DECIMAL.

3. Query data:

To query data in Oracle, you can use the following SQL statement:

SELECT * FROM employee WHERE emp_salary > 3000;

In DB2, the SQL statement for the same query is as follows:

SELECT * FROM employee WHERE emp_salary > 3000.00;

You also need to pay attention to the precision of decimals.

4. Update data:

To update data in Oracle, you can use the following SQL statement:

UPDATE employee SET emp_salary = 6000 WHERE emp_id = 101;

In DB2, the SQL statement for the same operation is as follows:

UPDATE employee SET emp_salary = 6000.00 WHERE emp_id = 101;

You need to also pay attention to the precision of decimals.

In summary, although Oracle and DB2 are both popular database management systems, there are still some minor differences in SQL operations. Through the specific code examples in this article, readers can better understand the similarities and differences between Oracle and DB2 in SQL operations, which will help them operate the database more flexibly and accurately in practical applications.

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