Posts (page 81)
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4 min readTo run multiple insert statements in a transaction in PostgreSQL, you can use the BEGIN, COMMIT, and ROLLBACK keywords to start, end, and cancel a transaction, respectively. Within the transaction block, you can include multiple insert statements to be executed as a single atomic operation. This ensures that if any of the insert statements fail, the transaction can be rolled back and none of the data will be committed to the database.
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6 min readIn PostgreSQL, you can store values from one procedure to another by using variables. You can declare variables within a procedure by using the DECLARE keyword followed by the variable name and data type. You can then assign values to these variables using the := operator.After storing a value in a variable in one procedure, you can pass that value to another procedure by either passing it as a parameter or by using a global variable.
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3 min readTo copy a CSV file into a Postgres Docker container, you can use the COPY command in a SQL statement. First, make sure the CSV file is accessible from the host machine running the Docker container.Next, start the Postgres Docker container and connect to the database using a client like psql. Then, you can run the COPY command in SQL to import the CSV file into a table.For example: COPY table_name FROM '/path/to/csv/file.
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5 min readTo calculate a percentage as an integer in PostgreSQL, you can use the following formula:(int)((value1 / value2) * 100)Where value1 is the numerator and value2 is the denominator. This formula calculates the percentage as a decimal value, which is then cast to an integer using the "int" function to get the final result as an integer.For example, if you want to calculate the percentage of 20 out of 50 as an integer:(int)((20 / 50) * 100) = (int)(0.
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4 min readTo convert a JSON array to a JSON object in PostgreSQL, you can use the json_object() function. This function allows you to create a JSON object from key-value pairs.You can first unnest the JSON array using the json_array_elements_text() function to get the elements of the array as text values. Then, you can use the json_object() function to construct a JSON object from these elements.
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5 min readTo update a JSON date field in PostgreSQL, you can use the jsonb_set function.
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5 min readThere are a few ways to improve the speed of PostgreSQL's INTERSECT operation.One approach is to make sure that you have properly indexed the columns that you are using in the INTERSECT query. This can help PostgreSQL quickly identify the common rows between the two data sets.Another tip is to analyze and optimize the query itself. This includes avoiding unnecessary calculations, filtering out rows that are not needed, and ensuring that the query is written in an efficient manner.
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3 min readTo combine multiple functions into one in PostgreSQL, you can create a new function that calls the other functions within it. This can be achieved by defining a new function and then calling the other functions using their names and arguments within the new function. This allows you to create a single function that performs multiple operations in a sequential manner. By combining functions in this way, you can streamline your code and make it more modular and reusable.
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7 min readTo use a json field in the WHERE clause in PostgreSQL, you can access the values within the JSON field by using the -> operator. This operator allows you to extract specific keys or values from the JSON data and compare them with other values in your query.
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4 min readIn Rust, you can fire an async callback by using the tokio or async-std runtime.To do this, you need to define a function that returns a Future and is marked as async. Inside this function, you can write your asynchronous code, such as making network requests or reading files.Once you have defined your async function, you can call it using the tokio::spawn or async_std::task::spawn function to fire off the asynchronous task.
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4 min readTo migrate an Access database to a PostgreSQL server, you can use a tool like PostgreSQL's foreign data wrapper or a third-party migration tool. You will first need to convert the schema of the Access database to match the PostgreSQL server's requirements, including data types, constraints, and indexes.
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5 min readTo fetch data in a given interval in PostgreSQL, you can use the BETWEEN keyword in your SQL query. The BETWEEN keyword allows you to specify a range of values and retrieve data that falls within that range.