Posts (page 117)
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2 min readTo remove all characters except 'e' in Oracle, you can use the REGEXP_REPLACE function. Here is an example query: SELECT REGEXP_REPLACE('Hello world!', '[^e]', '') AS result FROM dual; In this query, the REGEXP_REPLACE function is used to replace all characters that are not 'e' with an empty string. The '[^e]' pattern matches any character except 'e'. So, when you run this query, the result will be 'e'.
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6 min readTo use an Oracle sequence in Hibernate, you first need to define the sequence in your Oracle database. Once the sequence is created, you can map it to a Hibernate entity by using the @SequenceGenerator annotation on the entity's id field.You need to specify the name of the sequence, the allocation size (the number of sequence values that will be pre-allocated and stored in memory), and the catalog and schema of the sequence if necessary.
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5 min readTo insert data from multiple tables into one table in Oracle, you can use the INSERT INTO statement along with a SELECT statement that retrieves data from the multiple tables. You can use joins to link the tables and retrieve the data you want to insert into the target table. Make sure that the columns in the target table match the data types of the columns selected from the source tables.
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4 min readTo write a join query using Hibernate Criteria, you can use the createCriteria method to create a criteria object for each entity you want to join. Then, you can add restrictions and conditions to the criteria objects to specify the join conditions. Finally, you can use the createAlias method to create an alias for the joined entity and specify the join type. This will allow you to perform a join query using Hibernate Criteria.
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4 min readThe ALTER command is used when killing a session in Oracle because it allows for more control over the termination process. By using the ALTER command, you can explicitly tell Oracle how you want to end the session, whether you want to roll back any uncommitted transactions, or simply kill the session immediately. This helps prevent unexpected behavior and ensures that the session is terminated in a safe and controlled manner.
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5 min readIn Hibernate, a limit can be used to restrict the number of results returned by a query. This can be especially useful when dealing with large data sets and wanting to only retrieve a certain number of records at a time.To use a limit with Hibernate, you can simply add the "setMaxResults" method to your criteria query or HQL query. This method takes an integer parameter which specifies the maximum number of results to return.
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4 min readTo get a number as an alias in Oracle, you can use the AS keyword in your SQL query. You can give a number column or expression an alias by specifying the AS keyword followed by the alias name after the column or expression.For example, in a query like:SELECT 5 AS MyNumber FROM dual;This query will return a single row with a column named MyNumber containing the value 5. The AS keyword is used to assign the alias "MyNumber" to the number 5 in this case.
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5 min readYou can populate Elasticsearch with Hibernate Search by integrating Elasticsearch with your Hibernate Search implementation. By default, Hibernate Search uses Apache Lucene for indexing and searching data, but you can configure it to use Elasticsearch as the backend for storage and querying.To do this, you need to update your Hibernate Search configuration to use the Elasticsearch backend.
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6 min readTo perform a batch insert in an Oracle database, you can use the INSERT ALL statement followed by multiple INSERT INTO clauses. This allows you to insert multiple rows of data into one or more tables in a single statement, which can improve performance by reducing the number of round-trips between the database and the application.In addition to the INSERT ALL statement, you can also use the FORALL statement in PL/SQL for bulk processing of multiple rows in one go.
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7 min readTo populate two fields of an entity using Hibernate, you can create an instance of the entity class and set the values for the fields that you want to populate. Then, use Hibernate's session object to save the entity to the database. You can access the session object by calling the getSession() method on the Hibernate SessionFactory object.Once you have retrieved the session object, you can begin a transaction by calling the beginTransaction() method on the session object.
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6 min readTo convert exponent values in numbers in Oracle, you can use the TO_NUMBER function. This function allows you to convert a string representation of a number with an exponent (scientific notation) into a regular number format. For example, if you have a column with exponent values like '1.23E+2', you can convert it to a regular number format by using the TO_NUMBER function like this: SELECT TO_NUMBER('1.23E+2') FROM dual; This will return the value 123.
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4 min readTo join 3 tables using Hibernate Criteria, you can use createAlias() method multiple times to specify the associations between entities. By creating aliases for each association, you can navigate through the relationships and fetch the desired records.For example, if you have three entities A, B, and C with associations between A and B, and B and C, you can join all three tables using Hibernate Criteria as follows:Criteria criteria = session.createCriteria(A.class); criteria.