How to query numbers in oracle

Oracle database is a popular relational database management system around the world. It supports multiple data types, including numeric types, such as integers (INTEGER), decimals (FLOAT), double precision (DOUBLE PRECISION), etc. Querying numbers in an Oracle database is a basic operation. Let’s learn more about it below.

1. Oracle numeric data types

The numeric data types in Oracle database mainly include integer types and decimal types. The integer types include: NUMBER and INTEGER, and the decimal types include: FLOAT, DOUBLE PRECISION, BINARY FLOAT, and BINARY_DOUBLE. Let’s introduce them one by one below.

1. NUMBER type

The NUMBER type is the most commonly used number type in Oracle database, and its range is -10^124~10^124. The NUMBER type can store any number of digits. If the precision and scale are not specified, it will occupy the largest space. To specify the precision and scale, you can use the following method:

NUMBER(precision,scale)

In the above statement, precision represents the total number of digits (maximum 38), and scale represents the decimal The length of the section (maximum precision).

2. INTEGER type

The INTEGER type is used to store integers, and its range is -2^31 ~ 2^31-1. If a larger number range is required, the NUMBER type should be used. The INTEGER type does not require precision and scale to be specified.

3. FLOAT type

The FLOAT type is used to store floating point numbers, with a range of 1.17E^-38 ~ 3.4E^38 and a precision of 126 bits. Because floating point precision is unstable, be very careful when making comparisons.

4. DOUBLE PRECISION type

The DOUBLE PRECISION type is also used to store floating point numbers, with a range of 2.2E^-308 ~ 1.8E^308 and a precision of 15 digits. It is more precise than the FLOAT type and therefore more stable.

2. Oracle Numeric Query

With the above numerical types, we can perform numerical queries in the Oracle database. Oracle database provides a variety of query statements, commonly used ones include SELECT, WHERE, GROUP BY, HAVING, ORDER BY, etc.

1. SELECT query

In Oracle database, we can use the SELECT statement to query numbers. For example, we can query the total scores of all students using the following statement:

SELECT SUM(score) FROM student;

Here, the SUM function can sum the numbers in the specified column to get Total score.

2. WHERE query

The WHERE statement is used to specify query conditions, and it can be used for numeric type queries. For example, we can use the following statement to query all students with a score greater than 80:

SELECT * FROM student WHERE score > 80;

Here, the WHERE statement filters out records with a score greater than 80 , and then use a SELECT query to display the results.

3. GROUP BY query

The GROUP BY statement is used to group the same values. For example, we can use the following statement to query the average score based on class:

SELECT class, AVG(score) FROM student GROUP BY class;

Here, the GROUP BY statement groups the records according to class, and then Use the AVG function to calculate the average score for each class.

4. HAVING query

The HAVING statement is used to specify the filtering conditions of a certain number of functions. Unlike WHERE, HAVING filters the results grouped by GROUP BY. For example, we can use the following statement to query classes with an average score greater than 80:

SELECT class, AVG(score) FROM student GROUP BY class HAVING AVG(score) > 80;

Here, The HAVING statement filters out classes with an average score greater than 80.

5. ORDER BY query

The ORDER BY statement is used to sort query results. For example, we can use the following statement to sort from high to low scores:

SELECT * FROM student ORDER BY score DESC;

Here, DESC means descending order and ASC means ascending order.

3. Precautions for Oracle numeric queries

When performing Oracle numeric queries, you need to pay attention to the following points:

1. Be very careful when querying floating point numbers because of their accuracy Unstable.

2. The precision and scale of the numeric type need to be specified, otherwise it will occupy the largest space.

3. Function filtering after GROUP BY must use the HAVING statement for conditional judgment.

4. Be sure to use the ORDER BY statement to sort the results to ensure the accuracy of the results.

Summary

Oracle database is a very powerful relational database management system that supports a variety of number types, such as integers, decimals, etc. Oracle numeric query is a basic operation when using Oracle database. Common query statements include SELECT, WHERE, GROUP BY, HAVING, ORDER BY, etc. When performing digital queries, you need to pay attention to issues such as precision, scaling, and unstable floating-point precision to ensure the accuracy of query results.

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