能否結合 SQL 的 LIKE 和 IN 運算子來實現高效的模式匹配？

Combining SQL LIKE and IN Clauses for Enhanced Pattern Matching

In SQL, the LIKE operator is commonly utilized for pattern matching, enabling you to find rows that partially match a specified pattern. On the other hand, the IN operator allows you to check if a column's value matches any element within a predefined set. However, when combining these two operators, you may encounter certain limitations.

Consider the following scenario:

Question: Is it possible to combine the LIKE and IN clauses to efficiently match a column against a series of different strings in a single query? For example:

SELECT * FROM tablename WHERE column IN ('M510%', 'M615%', 'M515%', 'M612%');

Goal: Achieve pattern matching using multiple LIKE expressions without resorting to looping over an array of strings.

Solution:

While the LIKE IN construct is not explicitly supported, there are alternative approaches to achieve the desired result:

1. Using Substring and IN:

You can use the substring() function to extract a specified number of characters from the beginning of the column, and then employ the IN operator to check if the extracted substring matches any of the provided strings:

SELECT * FROM tablename WHERE substring(column,1,4) IN ('M510','M615','M515','M612')

In this example, the substring() function extracts the first four characters of the column, and the IN clause checks if the extracted substring matches any of the four specified strings.

2. Using CASE and WHEN:

Another approach involves utilizing the CASE and WHEN statements to evaluate multiple conditions:

SELECT * 
FROM tablename 
WHERE 
  CASE
    WHEN column LIKE 'M510%' THEN TRUE
    WHEN column LIKE 'M615%' THEN TRUE
    WHEN column LIKE 'M515%' THEN TRUE
    WHEN column LIKE 'M612%' THEN TRUE
    ELSE FALSE
  END;

This CASE statement evaluates each condition sequentially. If any of the conditions are met, the query returns the corresponding row.

These alternative approaches allow you to combine pattern matching with the convenience of the IN clause, facilitating more efficient and concise SQL queries.

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