Summary - Exposed SQL

Combine Table, transaction and CRUD to write a user database.

Summary - Exposed SQL

This group covered Exposed, Table, transaction, CRUD and join. They are the foundations of SQL database work in Kotlin.

You open a Database.connect, declare a table with object : Table(), wrap work in a transaction, do CRUD with insert/select/update/deleteWhere, and combine tables with innerJoin. Together they form a type safe data access layer.

Exercise Summary: Table and insert

Define object Users : Table() with val id = integer("id") and val name = varchar("name", 50). In main, open Database.connect, in a transaction block call Users.insert { it[name] = "Alex" } and print println("Summary ready").

Show example solution

object Users : Table() {
    val id = integer("id")
    val name = varchar("name", 50)
}

fun main() {
    Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver")
    transaction {
        Users.insert {
            it[name] = "Alex"
        }
        println("Summary ready")
    }
}

Test yourself

Which is used to remove a record?
- select
- insert
- update
- deleteWhere
Show answer

deleteWhere — deleteWhere removes records.
Match all Exposed concepts

Database.connect

Connection
Table

Table
transaction

Transaction
insert

Insert
innerJoin

Join

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