Introducing the include operation in Oracle queries

Oracle is a powerful database management system whose query statements can help us retrieve data efficiently. In actual development, we often need to query data that contains a certain keyword. This article will introduce the include operation in Oracle queries.

1. LIKE statement

In Oracle, one of the most basic ways to implement inclusion operations is through the LIKE statement. LIKE can add wildcard characters to the query to replace some characters or character sequences. For example, the following SQL query statement will return all records containing "an":

SELECT * FROM table_name WHERE column_name LIKE '%an%';

% means that it can replace any character or any sequence of characters. The query conditions here refer to all records that contain the "an" substring in the column_name field. Note that the LIKE clause is more efficient than regular expressions.

2. CONTAINS statement

Oracle provides the CONTAINS statement for more efficient inclusion operations. CONTAINS requires the use of a full-text index, so the index needs to be created in advance.

The following is an example of creating an index:

CREATE INDEX idx_table_name ON table_name(column_name) INDEXTYPE IS CTXSYS.CONTEXT;

In the above example, we created an index named idx_table_name, which performs a full-text index on the column_name column of the table_name table. Use CONTAINS query.

CONTAINS supports a variety of query forms, including single term query, phrase query, vocabulary approximate query, etc. The following is a simple query example:

SELECT * FROM table_name WHERE CONTAINS(column_name, 'an') > 0;

This sentence means to query all records containing "an" in the table_name table. The CONTAINS function returns an integer value. If this value is greater than 0, it means that the query result has been obtained.

3. REGEXP_LIKE statement

In addition to the LIKE and CONTAINS statements, Oracle also provides a regular expression query method - REGEXP_LIKE.

Regular expression is a powerful string matching tool, implemented in Oracle through the REGEXP_LIKE function. The following is an example of using regular expressions to query inclusion:

SELECT * FROM table_name WHERE REGEXP_LIKE(column_name, 'an.*');

This query will return all records starting with "an" in column_name. Among them, "." represents any character, and "*" represents 0 or more characters. If you want to match the exact "an", you can use "\b" to identify word boundaries.

Summary

The above introduces three methods on how to perform inclusion operations in Oracle. The most basic method is to use LIKE. If you need more efficient operation, you can use CONTAINS and regular expressions.

In the actual development process, the query method needs to be selected according to the specific situation. One thing to note is that CONTAINS and regular expression queries require the use of a full-text search index. Therefore, if the amount of data is not very large, a LIKE statement may be sufficient.

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