Complete Kotlin-classes representation of our SQL Grammar.

SQLAST.kt

sealed class SqlStatement

// Select statement
data class Select(
    val selectList: SelectList,
    val from: TableReference,
    val where: Condition? = null,
    val groupBy: GroupBy? = null,
    val orderBy: OrderBy? = null,
    val limit: Limit? = null
) : SqlStatement()

// Insert statement
data class Insert(
    val table: String,
    val columns: List<String>,
    val values: List<Expression>
) : SqlStatement()

// Update statement
data class Update(
    val table: String,
    val assignments: List<ColumnAssignment>,
    val where: Condition? = null
) : SqlStatement()

// Delete statement
data class Delete(
    val table: String,
    val where: Condition? = null
) : SqlStatement()

// SELECT LIST
sealed class SelectList
object AllColumns : SelectList()
data class ColumnList(val columns: List<String>) : SelectList()

// TABLE REFERENCE
data class TableReference(
    val table: String,
    val join: JoinClause? = null
)

data class JoinClause(
    val table: String,
    val on: Condition
)

// CONDITIONS
sealed class Condition
data class ComparisonCondition(
    val left: Expression,
    val operator: ComparisonOperator,
    val right: Expression
) : Condition()

data class LogicalCondition(
    val left: Condition,
    val operator: LogicalOperator,
    val right: Condition
) : Condition()

data class ParenthesizedCondition(val condition: Condition) : Condition()

// EXPRESSIONS
sealed class Expression
data class IdentifierExpression(val identifier: String) : Expression()
data class LiteralExpression(val literal: SqlLiteral) : Expression()
data class FunctionCallExpression(
    val functionName: String,
    val arguments: List<Expression>
) : Expression()
data class BinaryOperation(
    val left: Expression,
    val operator: Operator,
    val right: Expression
) : Expression()

// LITERALS
sealed class SqlLiteral
data class StringLiteral(val value: String) : SqlLiteral()
data class NumberLiteral(
    val number: Double) : SqlLiteral()
object NullLiteral : SqlLiteral()

// CLAUSES
data class ColumnAssignment(
    val column: String,
    val value: Expression
)

data class OrderBy(val terms: List<OrderTerm>)
data class OrderTerm(
    val column: String,
    val direction: OrderDirection? = null
)

data class GroupBy(val columns: List<String>)
data class Limit(val count: NumberLiteral)

// ENUMS
enum class ComparisonOperator {
    EQUAL, NOT_EQUAL, GREATER, LESS, GREATER_EQUAL, LESS_EQUAL
}

enum class LogicalOperator {
    AND, OR, NOT
}

enum class ArithmeticOperator {
    PLUS, MULTIPLY, DIVIDE
}

enum class OrderDirection { ASC, DESC }

// OPERATOR (combined)
sealed class Operator {
    data class Comparison(val op: ComparisonOperator) : Operator()
    data class Logical(val op: LogicalOperator) : Operator()
    data class Arithmetic(val op: ArithmeticOperator) : Operator()
}