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I have a table containing the fields group_id and group_type and I want to query the table for all the records having any tuple (group id, group type) from a list of tuples. For example, I want to be able to do something like: SELECT * FROM mytable WHERE (group_id, group_type) IN ( ("1234-567", 2), ("4321-765", 3), ("1111-222", 5))
16 sty 2024 · The thing to be aware of is that is a nested tuple not a 999-tuple or anything. That means you need to supply parameters like: (x.id, (x.name1, (x.name2, (x.something, (...))))) Or define another infix operator to assemble the parameters.
Tuples/records are like Cartesian product, because each value of a tuple or record contains a value from each of many underlying sets. Cartesian product is usually written with a product operator, \(\times\) or \(\Pi\).
In OCaml, you can work with various SQL databases such as SQLite, PostgreSQL, or MySQL using libraries like `ocaml-sqlite3`, `ocaml-postgresql`, or `ocaml-mysql`. These libraries provide support for querying and manipulating data, including the ability to create and manage indexes.
Mssql is an Async OCaml SQL Server library, currently using FreeTDS. Features. Queries run in a background thread and play nicely with Async (assuming you're pinning freetds so it releases the runtime lock) Supports single connections or connection pools; Supports automatic conversions for common data types
Tuples. Every function in OCaml takes exactly one value and returns exactly one result. For instance, our squareRoot function takes one float value and returns one float value. The advantage of always taking one argument and returning one result is that the language is extremely uniform.
Tuples. Here is a tuple containing two values, also known as a pair. # (3, 'K');;-: int * char = (3, 'K') That pair contains the integer 3 and the character 'K'; its type is int * char. The * symbol stands for product type. This generalises to tuples with 3 or more elements. For instance, (6.28, true, "hello") has type float * bool * string.
