Posts (page 84)
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3 min readTo set a maximum value for a column in PostgreSQL, you can use the CHECK constraint when creating the table. This constraint allows you to specify a condition that must be met for every row in the table.
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8 min readTo convert a MongoDB Decimal128 value to JSON in Rust, you can use the bson and serde_json crates. First, you will need to parse the Decimal128 value from your MongoDB document using the bson crate. Once you have the Decimal128 value, you can convert it to a JSON value using the serde_json crate.
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4 min readTo create a type using a specified schema in PostgreSQL, you can use the command CREATE TYPE followed by the type name and the schema name. For example:CREATE TYPE schema_name.type_name AS ( attribute1 data_type, attribute2 data_type, ... );This command will create a new type with the specified attributes in the specified schema. Make sure to replace schema_name and type_name with your desired schema and type names, and data_type with the appropriate data types for your attributes.
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7 min readTo copy a PostgreSQL function, you can use the CREATE FUNCTION command followed by the function name, input parameters, and the definition of the function. You can also use pg_get_functiondef to get the definition of an existing function and then modify it as needed to create a new function. Make sure to specify a new name for the copied function to avoid conflicts with existing functions.
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3 min readTo convert a string to a valid JSON in Rust, you can use the serde_json crate. First, you need to add serde_json as a dependency in your Cargo.toml file: [dependencies] serde = "1.0" serde_json = "1.0" Then, you can use the serde_json::from_str function to convert a JSON string to a JSON value.
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7 min readTo update data with a case conditional in PostgreSQL, you can use the CASE statement within the UPDATE query. The CASE statement allows you to perform different actions based on specific conditions.
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6 min readIn Rust, you can define a function that accepts multiple types by using generics. Generics allow you to write code that can work with different types without specifying them explicitly. You can define a generic function by using angle brackets <> and specifying the types within them. For example, you can define a function like this: fn my_function<T>(value: T) { // function implementation here } In this example, T is a generic type parameter that can be any type.
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4 min readTo sync data between PostgreSQL and SQLite, you can follow these general steps:Connect to both databases using their respective connection methods.Identify which data needs to be synchronized between the two databases.Write scripts or queries to extract the necessary data from one database and insert it into the other database.Make sure to handle any data type conversions or formatting differences between PostgreSQL and SQLite.
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4 min readIn PostgreSQL, you can calculate the date of birth from a full age by using the AGE() function along with the current date. The AGE() function returns the difference between two dates as an interval, which can then be used to calculate the date of birth.For example, you can get the date of birth from a full age of 30 years by subtracting 30 years from the current date.
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3 min readIn Rust, you can assert the type of a variable in a macro by using the assert_eq! macro. This macro takes two arguments, the expected type and the actual type of the variable. If the two types are not equal, the macro will fail at compile time. This can be useful for ensuring that the input to your macro is of the correct type, and can help catch type errors early in the development process.
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5 min readTo join tables with a condition in PostgreSQL, you can use the syntax of the JOIN keyword followed by the ON keyword and the condition. The condition typically involves comparing a column from one table to a column from another table to establish the relationship between the two tables.For example, you can join two tables, such as "employees" and "departments," based on the common column "department_id" by using the following query:SELECT employees.employee_id, employees.
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6 min readTo run multiple dynamic queries in a PostgreSQL function, you can use the EXECUTE command along with string concatenation to build and execute the SQL queries dynamically within the function.First, you need to define a variable to hold the dynamic query string. Then, use the EXECUTE command to run the dynamic query. You can pass parameters to the dynamic query using the USING clause with EXECUTE.