Understanding Oracle SQL and Matching Standard IDs to Student Registration IDs

As a technical blogger, I have encountered numerous queries over the years where users sought to match or map values between two tables in an Oracle database. In this blog post, we will explore one such scenario involving standard IDs from the student_table and student registration IDs from the Reg_table. Specifically, we’ll delve into how to use the LIKE function and its variations to achieve this mapping.

Background on Oracle SQL and Table Joins

Before diving into the solution, it’s essential to understand the basics of Oracle SQL and table joins. In Oracle, a database consists of multiple tables, which are used to store data. A table is essentially a two-dimensional array of rows and columns. When working with Oracle databases, we use Structured Query Language (SQL) commands to interact with these tables.

Table joins allow us to combine rows from two or more tables based on common columns between them. The three primary types of table joins are:

• INNER JOIN: Returns records that have matching values in both tables.
• LEFT JOIN (or LEFT OUTER JOIN): Returns all records from the left table, and the matched records from the right table if they exist.
• RIGHT JOIN (or RIGHT OUTER JOIN): Similar to a LEFT JOIN, but returns all records from the right table.

In our scenario, we’ll use a LEFT JOIN to match standard IDs from the student_table with student registration IDs from the Reg_table.

The Problem and the Solution

Let’s re-examine the problem. We have two tables:

• Student Table (student_table):

  • STD_ID: A unique identifier for each student.
  • Other columns may contain additional information about students (e.g., names, addresses).

• Registration Table (Reg_table):

  • Student_reg_ID: A unique identifier assigned to each student upon registration.
  • Reference: A value that corresponds to the standard ID from the student_table.

Our goal is to match the standard IDs with their corresponding student registration IDs and output a table with both values.

Using the LIKE Function

Initially, we were considering using the LIKE function in our query. While this can be an effective way to perform pattern matching, it has its limitations when dealing with large datasets or specific scenarios like ours.

-- Basic LIKE example
SELECT *
FROM student_table st
JOIN Reg_table rt ON rt.Reference LIKE '%' || st.STD_ID || '%';

However, using the LIKE function with a wildcard (%) for every standard ID in our table would result in a lengthy query that may not be efficient or easy to maintain. Instead, we can use Oracle’s advanced string functions and join operations to achieve the desired mapping.

Using Oracle Advanced String Functions

Oracle provides several advanced string functions that can help us solve this problem more efficiently:

• REGEXP_LIKE: Used for regular expression pattern matching.
• TO_CHAR or TO_NUMBER: Used for converting data types (e.g., numbers to strings).

We’ll explore these functions and see how they can be applied to our scenario.

Using REGEXP_LIKE

One approach is to use the REGEXP_LIKE function to enforce an exact match when joining:

-- Using REGEXP_LIKE for exact matching
SELECT st.STD_ID, rt.Student_reg_ID
FROM student_table st
LEFT JOIN Reg_table rt
ON REGEXP_LIKE(rt.Reference, '(^|\s)' || st.STD_ID || '(\s|$)');

In this example, we’re using a regular expression pattern to ensure that the standard ID from the student_table is present exactly in the Reference column of the Reg_table. The ( ^ | \s ) part matches either the start of the string (^) or any whitespace character (\s), while the (\s|$) part matches any whitespace characters at the end of the string ($). This allows us to ensure that only exact matches are considered.

Converting Data Types

If your standard IDs are numeric values, you’ll need to convert them to strings using Oracle’s TO_CHAR function before performing the LIKE comparison:

-- Converting numeric STD_ID to string for LIKE comparison
SELECT st.STD_ID, rt.Student_reg_ID
FROM student_table st
LEFT JOIN Reg_table rt
ON REGEXP_LIKE(rt.Reference, '(^|\s)' || TO_CHAR(st.STD_ID) || '(\s|$)');

By converting the numeric STD_ID to a string using TO_CHAR, we can perform the LIKE comparison without any issues related to data type mismatch.

Example Use Case

To illustrate how this solution works in practice, let’s consider an example dataset for our two tables:

Student Table (student_table):

Registration Table (Reg_table):

Using the solution provided, we can join these two tables based on exact matches between standard IDs and student registration IDs:

-- Joining tables with REGEXP_LIKE for exact matching
SELECT st.STD_ID, rt.Student_reg_ID
FROM student_table st
LEFT JOIN Reg_table rt
ON REGEXP_LIKE(rt.Reference, '(^|\s)' || st.STD_ID || '(\s|$)');

The resulting table will contain both standard IDs and their corresponding student registration IDs:

Conclusion

In this tutorial, we explored how to solve the problem of matching standard IDs with student registration IDs using Oracle’s advanced string functions and join operations. By leveraging REGEXP_LIKE, TO_CHAR or TO_NUMBER, and LEFT JOINs, we can efficiently map these unique identifiers across two tables.

When working with large datasets or complex data relationships, understanding how to effectively use Oracle’s advanced features is crucial for developing efficient and scalable database solutions.

Last modified on 2024-06-09