Posts - Page 142 (page 142)
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5 min readIn PostgreSQL, you can implement a constraint on a table to enforce certain rules or conditions on the data stored in that table.To implement a constraint in PostgreSQL, you can use the ALTER TABLE statement with the ADD CONSTRAINT clause. For example, you can add a NOT NULL constraint to a column to ensure that it always contains a value, or you can add a UNIQUE constraint to a column to ensure that all values in that column are unique.
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7 min readIn Hibernate, you can change the related object to another by simply updating the reference of the object in the parent object. This can be done by setting the new related object to the appropriate field in the parent object and then saving the parent object using the session.update() method.
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4 min readIn PostgreSQL, you can query by date and time using the date and time functions provided by the database. You can use functions like CURRENT_DATE to get the current date, and CURRENT_TIME to get the current time. To query records based on a specific date or range of dates, you can use the DATE data type and compare it using operators like = or BETWEEN. Similarly, you can query records based on a specific time or range of times by using the TIME data type and comparison operators.
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5 min readTo disable a trigger using Hibernate, you can use the following steps:Disable the trigger in the database by running a SQL query or using a database management tool.Update the Hibernate mapping file to exclude the trigger from being fired during entity operations.If the trigger is associated with a specific entity or table, you can disable it by modifying the relevant entity class or mapping file.
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6 min readTo get a column value with a custom array in PostgresSQL, you can use the following syntax:SELECT column_name[array_index] FROM table_name;Replace "column_name" with the name of the column you want to retrieve values from, "array_index" with the index of the array element you want to retrieve, and "table_name" with the name of the table where the data is stored.
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4 min readTo loop over an array using PostgreSQL JSON functions, you can use the json_array_elements function to unnest the array elements and then use a loop construct such as FOR ... IN or SELECT ... INTO to iterate over each element. By using this approach, you can access and manipulate each element of the array individually within your SQL queries.[rating:e727dd3b-20e7-430f-ba0b-7c16ada6dc22]How to extract values from a JSON array in PostgreSQL.
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5 min readIn Hibernate, you can make a string case insensitive in a query by using the lower() function. This function converts a string to lowercase, allowing you to compare strings in a case-insensitive manner. Here is an example of how to use the lower() function in a Hibernate query: // Create a Hibernate query Query query = session.createQuery("from EntityName where lower(propertyName) = :value"); // Set the parameter value query.setParameter("value", searchValue.
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5 min readIn PostgreSQL, the best way to copy or insert data on cascade is to use the CASCADE option in a foreign key constraint. When a foreign key constraint with CASCADE option is specified between two tables, any changes to the referenced table's primary key will automatically propagate to the referencing table's foreign key columns. This means that when you insert or update data in the referenced table, the changes will be automatically reflected in the referencing table.
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5 min readIn Hibernate, mapping a single table to multiple tables can be achieved using the concept of inheritance mapping. This can be done through the use of different strategies such as table per class, table per subclass, or table per concrete class.Table per class strategy involves creating a separate table for each class in the inheritance hierarchy, with each table containing the columns specific to that class.
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3 min readTo reset the password for a PostgreSQL user, you can follow these steps. First, you need to access the PostgreSQL command line interface by opening a terminal window. Then, you can log in as the PostgreSQL superuser by using the command sudo -u postgres psql.
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4 min readTo disable the collection cache for Hibernate, you can set the "hibernate.cache.use_second_level_cache" property to "false" in your Hibernate configuration file. This will prevent Hibernate from caching collections in the second level cache. Additionally, you can disable the query cache by setting the "hibernate.cache.use_query_cache" property to "false".
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4 min readTo insert a new parameter into a column in PostgreSQL, you can use the ALTER TABLE statement. This statement allows you to add a new parameter to an existing column in a table. You can specify the name of the column where you want to insert the new parameter, along with the data type and any other constraints that may be required. Additionally, you can provide a default value for the new parameter if needed.