Posts (page 79)
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4 min readTo group separately by multiple columns in PostgreSQL, you can use the GROUP BY clause along with the columns you want to group by. This allows you to combine rows that have the same values in those columns and perform aggregate functions on the grouped data. By specifying multiple columns in the GROUP BY clause, you can group the data separately based on the unique combinations of values in those columns.
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7 min readTo convert PostgreSQL results to JSON, you can use the json_agg function which aggregates rows into a JSON array. You can also use the row_to_json function to convert individual rows into JSON objects. This way, you can easily transform the query results into a JSON format that can be used for further processing or storage. Additionally, you can use the json_build_object function to construct JSON objects with specific keys and values based on the query results.
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4 min readIn PostgreSQL, you can add a condition to the count function by using the CASE statement in conjunction with the count function. By using the CASE statement, you can specify the condition that you want to apply to the count function. For example, if you want to count only the rows that meet a certain condition, you can do so by using a CASE statement within the count function. This allows you to customize the behavior of the count function based on your specific requirements.
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5 min readIn PostgreSQL, you can combine a date with a string by using the CONCAT function. To do this, you simply need to convert the date to a string using the TO_CHAR function, and then concatenate it with the desired string using the CONCAT function.
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6 min readTo enforce clients to use SSL for PostgreSQL, you can configure the PostgreSQL server to require SSL connections by setting the ssl parameter to on in the postgresql.conf file. You can also specify that clients must use SSL by setting the sslmode parameter in the connection string to require or verify-full. This will ensure that all clients connecting to the PostgreSQL server must use SSL encryption for secure communication.
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7 min readTo create an input type file in a canvas element to upload an image, you can start by adding an input element of type "file" to your HTML code. This input element allows users to select an image file from their local system.Next, you'll need to add JavaScript code to handle the file upload. When a user selects an image file, you can use the FileReader API to read the contents of the selected file.
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4 min readTo convert a PostgreSQL query to BigQuery, you will need to make some adjustments to the syntax and take into consideration the differences between the two databases.One of the main differences between PostgreSQL and BigQuery is the use of functions and operators. BigQuery has its own set of functions and operators, so you may need to modify your PostgreSQL query to use the equivalent functions in BigQuery.Another difference is the syntax for joining tables.
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4 min readYou can force a canvas refresh in JavaScript by using the context.clearRect() method to clear the canvas and then redrawing the content you want to display. You can also set the canvas width or height to itself, which will force the canvas to clear and refresh. Another option is to use the context.save() and context.restore() methods to reset the canvas state. Additionally, you can use the context.drawImage() method to redraw an image on the canvas to trigger a refresh.
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6 min readTo send messages from PostgreSQL to RabbitMQ, you can use a combination of triggers and functions.First, you need to create a trigger on the table that you want to send messages from. This trigger will be responsible for calling a function whenever a new row is inserted, updated, or deleted in the table.Next, you need to create a function that actually sends the message to RabbitMQ. This function can use a library like pika to establish a connection to the RabbitMQ server and send the message.
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5 min readIn CSS, the z-index property can be used to control the stacking order of elements on a webpage. When working with canvas elements, the z-index can also be used to control the order in which different canvas elements are displayed on the page.To set the z-index of a canvas element, you can simply apply the z-index property to the CSS of that element.
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5 min readTo replace values in a column in a table by condition in PostgreSQL, you can use the UPDATE statement combined with a CASE statement.Here is an example query that demonstrates how you can replace values based on a specific condition: UPDATE table_name SET column_name = CASE WHEN condition THEN new_value ELSE column_name END; In this query:table_name is the name of the table you want to update.column_name is the name of the column you want to update.
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6 min readIn order to achieve smooth movement of a player in a canvas game, there are a few techniques you can employ. One common approach is to use a combination of keyboard input handling and frame rate management. By capturing keyboard input and updating the player's position on each frame, you can create the illusion of smooth movement.Another important aspect is to use interpolation or lerping to smoothly transition the player's position from one frame to the next.