Posts (page 114)
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6 min readRow_number() is a powerful function in Oracle SQL that assigns a unique sequential integer to each row within a partition of a result set. This function is commonly used in analytic queries to rank or order data based on specific criteria.To use row_number() in Oracle SQL, you need to include it as part of a SELECT statement with an OVER clause to define the partitioning and ordering of the rows. The basic syntax for using row_number() is as follows:SELECT column1, column2, ...
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![How to Map A Postgresql Text[] With Hibernate? preview](https://cdn.blogweb.me/1/66ad8432e67b5bed7820e3cd_242bc8bf0a.png)
6 min readTo map a PostgreSQL text[] array with Hibernate, you can use the @ElementCollection annotation in your entity class along with specifying the @CollectionTable and @Column annotations to map the array to the corresponding database table and column. Make sure to also specify the type of the array elements using the @Type annotation. Additionally, you may need to implement a custom user type to handle the conversion between the PostgreSQL array and Java array in Hibernate.
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3 min readIn Oracle, the equivalent for @@error in SQL Server is the SQLCODE function. SQLCODE returns the numeric error code for the last executed SQL statement. It is often used in conjunction with the SQLERRM function, which returns the error message associated with the error code. Together, SQLCODE and SQLERRM can be used to handle and display errors in Oracle PL/SQL code.[rating:dc3bb8f1-bf14-46f8-a39b-16fc925c6a8c]How to rollback transactions in case of errors in Oracle.
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5 min readConcurrency in Hibernate can be implemented by utilizing optimistic locking mechanisms. This is achieved by adding a version attribute to the entity class which is annotated with @Version. When an entity is updated, Hibernate checks if the version attribute in the database matches the one in the entity being updated. If they do not match, a StaleObjectStateException is thrown which indicates that another user has already made changes to the entity.
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8 min readConverting PostgreSQL code to Oracle SQL involves making certain syntax adjustments since the two database systems have different SQL dialects. Some key differences to keep in mind include:Oracle SQL uses "dual" table for selecting literal values without a table, whereas PostgreSQL uses "SELECT" with "FROM" clause. Oracle SQL uses "||" for string concatenation, whereas PostgreSQL uses "CONCAT".
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5 min readTo pass parameters to a custom function in Hibernate, you can use the setParameter method of the Query interface. This method allows you to set parameters for your custom function by specifying the parameter name and value. You can then use these parameters within your custom function logic to perform operations such as filtering, grouping, or ordering data in your query results.
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5 min readTo change a number column to a date in Oracle, you can use the TO_DATE function to convert the number to a date format. You need to specify the number format and the date format in the function.
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5 min readIn Hibernate, the mapping between a database table and a persistence class is defined using XML mapping files or annotations. Each persistent class in Hibernate corresponds to a table in the database, and each property in the class corresponds to a column in the table.To find the class-table mapping for a particular entity in Hibernate, you can look at the mapping file (usually in the form of an XML file) or the annotations used in the entity class.
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3 min readTo replace a string using REGEXP_REPLACE in Oracle, you need to specify the input string, the regular expression pattern to match, the replacement string, and any optional flags for the regex operation.
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7 min readTo get an Oracle connection from a Hibernate connection, you can first obtain the Hibernate Session object using the sessionFactory.getCurrentSession() method. Once you have the Session object, you can access the underlying JDBC Connection object by calling session.connection(). This will give you a raw JDBC Connection that you can then cast to an Oracle Connection using a typecast.
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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.