Posts (page 113)
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4 min readTo check if two HashMaps are identical in Rust, you can compare their key-value pairs. First, you can check if the two HashMaps have the same length using the len() method. Then, iterate over one of the HashMaps and check if each key-value pair exists in the second HashMap using the get() method. If all key-value pairs match, then the two HashMaps are identical. You can create a function to encapsulate this logic and return a boolean value indicating whether the HashMaps are identical or not.
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8 min readIn Hibernate, to join separate table data columns in a query, you can use the HQL (Hibernate Query Language) or Criteria API. By using HQL, you can write a SQL-like query to select specific columns from multiple tables and then create a custom result transform to combine the data from the separate tables. Alternatively, you can use the Criteria API to join the tables using criteria and then select the desired columns to be fetched in the result set.
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4 min readTo get specific data from XML in an Oracle table, you can use the XMLType data type and XML functions provided by Oracle. First, you need to query the XML column in the table using the XMLType constructor function. Then, you can use XPath expressions to navigate through the XML structure and extract the specific data you need. For example, you can use the extractValue() function to retrieve a specific element or attribute value from the XML document.
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4 min readIn Hibernate, a 1:n relationship between two entities can be created by annotating the entities with the appropriate mapping annotations. One entity will have a reference to the other entity, indicating a one-to-many relationship.To create a 1:n relationship with Hibernate, you can use the @OneToMany annotation on the parent entity's field that represents the collection of child entities.
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7 min readTo query by date in Oracle, you can use the TO_DATE function to convert a date string into a date format that Oracle can understand.
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6 min readIn Hibernate, mapping an entity to more than one entity type can be achieved through inheritance mapping strategies. Hibernate supports four inheritance mapping strategies: table per hierarchy, table per concrete class, table per subclass, and table per class.To properly map an entity to more than one entity type, you need to define a base entity class and then create subclasses for each entity type you want to map to.
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4 min readIf you want to pretty format JSON in Oracle, you can use the JSON_OBJECT function, which allows you to create JSON objects in a structured way. You can also use the JSON_QUERY function to extract values from a JSON document and format them in a readable way. Additionally, you can use the JSON_ARRAYAGG function to aggregate values from multiple rows into a single JSON array. These functions can help you format JSON data in a more organized and visually appealing manner.
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7 min readIn Hibernate, if you need to regenerate deleted sequence numbers, you can do so by adjusting the hibernate_sequence table in the database. Start by locating the hibernate_sequence table and find the respective row for the deleted sequence number. You can manually update the value in the next_val column to the desired sequence number that you want to regenerate.
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5 min readTo create an alias from a select result in Oracle, you can use the AS keyword followed by the desired alias name. For example, in a select statement like SELECT column_name AS alias_name FROM table_name;, "column_name" is the original name of the column and "alias_name" is the alias name you want to give to that column in the result set. Aliases can be helpful for making your query results more readable and for giving descriptive and easily identifiable names to your data.
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8 min readTo map a foreign key with Hibernate, you can use the @ManyToOne or @OneToOne annotation in your entity class. These annotations indicate that the entity has a many-to-one or one-to-one relationship with another entity. You can specify the target entity and the foreign key column using attributes of these annotations. Additionally, you can use the mappedBy attribute to specify the mapping on the other side of the relationship.
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3 min readTo create a function in Oracle, you first need to use the CREATE FUNCTION statement followed by the function name and parameters. Inside the function, you can write the logic for what the function should do, such as calculations or data manipulation. Make sure to specify the data type that the function will return. Once the function is defined, you can call it in SQL statements like any other function. Make sure to use proper error handling and testing to ensure the function works as expected.
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6 min readTo map results of a Hibernate query to a DTO object, you can create a constructor in the DTO class that can accept the result object as arguments in the same order as they are returned by the query. Then, in your Hibernate query, you can use the new keyword followed by the fully-qualified name of the DTO class with the arguments to instantiate the DTO object with the query results. Alternatively, you can also use a projection in the query to directly map the query results to the DTO object.