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Add support for MSSQL IF/ELSE statements. #1791

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Merged
merged 10 commits into from
Apr 6, 2025
Merged

Add support for MSSQL IF/ELSE statements. #1791

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fbbffea
Add support for MSSQL IF/ELSE statements.
Apr 1, 2025
e610c8b
Wrap tokens attached to AST nodes in AttachedToken.
Apr 2, 2025
54d2325
Address cargo fmt style errors.
Apr 2, 2025
1d74a26
Avoid dialect-specific AST nodes.
Apr 4, 2025
90acac0
Address linter errors.
Apr 4, 2025
6a0deb6
Fix no-std build.
Apr 4, 2025
647c84b
One more linter fix.
Apr 4, 2025
535793d
Use exhaustive let-match in Spanned impls.
Apr 5, 2025
56b63be
Merge branch 'main' into mssql-if-else
Apr 5, 2025
6a6e561
Fix (my own) lint error from a previous PR.
Apr 5, 2025
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203 changes: 140 additions & 63 deletions src/ast/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,8 @@ use serde::{Deserialize, Serialize};
#[cfg(feature = "visitor")]
use sqlparser_derive::{Visit, VisitMut};

use crate::tokenizer::Span;
use crate::keywords::Keyword;
use crate::tokenizer::{Span, Token};

pub use self::data_type::{
ArrayElemTypeDef, BinaryLength, CharLengthUnits, CharacterLength, DataType, EnumMember,
Expand Down Expand Up @@ -2118,20 +2119,23 @@ pub enum Password {
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
pub struct CaseStatement {
/// The `CASE` token that starts the statement.
pub case_token: AttachedToken,
pub match_expr: Option<Expr>,
pub when_blocks: Vec<ConditionalStatements>,
pub else_block: Option<Vec<Statement>>,
/// TRUE if the statement ends with `END CASE` (vs `END`).
pub has_end_case: bool,
pub else_block: Option<ConditionalStatements>,
/// The last token of the statement (`END` or `CASE`).
pub end_case_token: AttachedToken,
}

impl fmt::Display for CaseStatement {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let CaseStatement {
case_token: _,
match_expr,
when_blocks,
else_block,
has_end_case,
end_case_token: AttachedToken(end),
} = self;

write!(f, "CASE")?;
Expand All @@ -2145,116 +2149,189 @@ impl fmt::Display for CaseStatement {
}

if let Some(else_block) = else_block {
write!(f, " ELSE ")?;
format_statement_list(f, else_block)?;
write!(f, " {else_block}")?;
}

write!(f, " END")?;
if *has_end_case {
write!(f, " CASE")?;

if let Token::Word(w) = &end.token {
if w.keyword == Keyword::CASE {
write!(f, " CASE")?;
}
}

Ok(())
}
}

/// An `IF` statement.
///
/// Examples:
/// ```sql
/// IF TRUE THEN
/// SELECT 1;
/// SELECT 2;
/// ELSEIF TRUE THEN
/// SELECT 3;
/// ELSE
/// SELECT 4;
/// END IF
/// ```
///
/// [BigQuery](https://cloud.google.com/bigquery/docs/reference/standard-sql/procedural-language#if)
/// [Snowflake](https://docs.snowflake.com/en/sql-reference/snowflake-scripting/if)
#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
pub struct IfStatement {
pub if_block: ConditionalStatements,
pub elseif_blocks: Vec<ConditionalStatements>,
pub else_block: Option<Vec<Statement>>,
pub enum IfStatement {
/// An `IF ... THEN [ELSE[IF] ...] END IF` statement.
///
/// Example:
/// ```sql
/// IF TRUE THEN
/// SELECT 1;
/// SELECT 2;
/// ELSEIF TRUE THEN
/// SELECT 3;
/// ELSE
/// SELECT 4;
/// END IF
/// ```
///
/// [BigQuery](https://cloud.google.com/bigquery/docs/reference/standard-sql/procedural-language#if)
/// [Snowflake](https://docs.snowflake.com/en/sql-reference/snowflake-scripting/if)
IfThenElseEnd {
/// The `IF` token that starts the statement.
if_token: AttachedToken,
if_block: ConditionalStatements,
elseif_blocks: Vec<ConditionalStatements>,
else_block: Option<ConditionalStatements>,
/// The `IF` token that ends the statement.
end_if_token: AttachedToken,
},
/// An MSSQL `IF ... ELSE ...` statement.
///
/// Example:
/// ```sql
/// IF 1=1 SELECT 1 ELSE SELECT 2
/// ```
///
/// [MSSQL](https://learn.microsoft.com/en-us/sql/t-sql/language-elements/if-else-transact-sql?view=sql-server-ver16)
MsSqlIfElse {
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Would it be possible to merge the representation to be shared by both? Something like this roughly I'm thinking

enum StatementBlock {
  Expr(Expr),
  Statements(Vec<Statements>),
  Begin(Vec<Statements>)
}

pub struct IfStatement {
    pub condition: Expr,
    pub if_block: StatementBlock,
    pub elseif_blocks: Vec<StatementBlock>,
    pub else_block: Option<StatementBlock>,
}

Ideally we avoid introducing dialect specific nodes in the AST

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Thank you for your feedback. I pushed further changes to avoid the dialect-specific AST nodes.

if_token: AttachedToken,
condition: Expr,
if_statements: MsSqlIfStatements,
else_statements: Option<MsSqlIfStatements>,
},
}

impl fmt::Display for IfStatement {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let IfStatement {
if_block,
elseif_blocks,
else_block,
} = self;
match self {
IfStatement::IfThenElseEnd {
if_token: _,
if_block,
elseif_blocks,
else_block,
end_if_token: _,
} => {
write!(f, "{if_block}")?;

write!(f, "{if_block}")?;
if !elseif_blocks.is_empty() {
write!(f, " {}", display_separated(elseif_blocks, " "))?;
}

if !elseif_blocks.is_empty() {
write!(f, " {}", display_separated(elseif_blocks, " "))?;
}
if let Some(else_block) = else_block {
write!(f, " {else_block}")?;
}

if let Some(else_block) = else_block {
write!(f, " ELSE ")?;
format_statement_list(f, else_block)?;
}
write!(f, " END IF")?;

Ok(())
}
IfStatement::MsSqlIfElse {
if_token: _,
condition,
if_statements,
else_statements,
} => {
write!(f, "IF {condition} {if_statements}")?;

write!(f, " END IF")?;
if let Some(els) = else_statements {
write!(f, " ELSE {els}")?;
}

Ok(())
Ok(())
}
}
}
}

/// Represents a type of [ConditionalStatements]
/// (MSSQL) Either a single [Statement] or a block of statements
/// enclosed in `BEGIN` and `END`.
#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
pub enum ConditionalStatementKind {
/// `WHEN <condition> THEN <statements>`
When,
/// `IF <condition> THEN <statements>`
If,
/// `ELSEIF <condition> THEN <statements>`
ElseIf,
pub enum MsSqlIfStatements {
/// A single statement.
Single(Box<Statement>),
/// ```sql
/// A logical block of statements.
///
/// BEGIN
/// <statement>;
/// <statement>;
/// ...
/// END
/// ```
Block {
begin_token: AttachedToken,
statements: Vec<Statement>,
end_token: AttachedToken,
},
}

impl fmt::Display for MsSqlIfStatements {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
MsSqlIfStatements::Single(stmt) => stmt.fmt(f),
MsSqlIfStatements::Block { statements, .. } => {
write!(f, "BEGIN ")?;
format_statement_list(f, statements)?;
write!(f, " END")
}
}
}
}

/// A block within a [Statement::Case] or [Statement::If]-like statement
///
/// Examples:
/// Example 1:
/// ```sql
/// WHEN EXISTS(SELECT 1) THEN SELECT 1;
/// ```
///
/// Example 2:
/// ```sql
/// IF TRUE THEN SELECT 1; SELECT 2;
/// ```
///
/// Example 3:
/// ```sql
/// ELSE SELECT 1; SELECT 2;
/// ```
#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
pub struct ConditionalStatements {
/// The condition expression.
pub condition: Expr,
/// The start token of the conditional (`WHEN`, `IF`, `ELSEIF` or `ELSE`).
pub start_token: AttachedToken,
/// The condition expression. `None` for `ELSE` statements.
pub condition: Option<Expr>,
/// Statement list of the `THEN` clause.
pub statements: Vec<Statement>,
pub kind: ConditionalStatementKind,
}

impl fmt::Display for ConditionalStatements {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let ConditionalStatements {
condition: expr,
start_token: AttachedToken(start),
condition,
statements,
kind,
} = self;

let kind = match kind {
ConditionalStatementKind::When => "WHEN",
ConditionalStatementKind::If => "IF",
ConditionalStatementKind::ElseIf => "ELSEIF",
};
let keyword = &start.token;

write!(f, "{kind} {expr} THEN")?;
if let Some(expr) = condition {
write!(f, "{keyword} {expr} THEN")?;
} else {
write!(f, "{keyword}")?;
}

if !statements.is_empty() {
write!(f, " ")?;
Expand Down
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