> ## Documentation Index > Fetch the complete documentation index at: https://powersync-custom-checkpoints-rollout-docs.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Grammar Reference (Sync Streams) > Railroad diagram reference for the SQL grammar supported in Sync Streams queries. This page is a formal grammar reference for Sync Streams: it shows the syntax the compiler accepts using railroad diagrams. This page complements the [Supported SQL](/sync/supported-sql) guide, which explains in prose what you can write, with examples and restrictions. **When to use this page:** If you need to check whether a construct is valid, see how rules nest (e.g. subqueries, CTEs, JOINs), or you're used to grammar specs, use the diagrams and the "Used by" / "References" links to navigate. For most users just getting started, see [Supported SQL](/sync/supported-sql) and [Writing Queries](/sync/streams/queries). ## SelectStatement ```sql theme={null} SELECT id, name FROM users WHERE active = true ``` SelectStatement syntax diagram

**References:** [FromSource](#fromsource), [JoinClause](#joinclause), [SelectItem](#selectitem), [WhereClause](#whereclause) *** ## SelectItem ```sql theme={null} name AS user_name ``` SelectItem syntax diagram

**References:** [Expression](#expression), [Identifier](#lexical-rules), [Reference](#reference) [SelectStatement](#selectstatement), [Subquery](#subquery) *** ## Reference ```sql theme={null} users.id ``` Reference syntax diagram

**References:** [Identifier](#lexical-rules) [SelectItem](#selectitem), [TableSource](#tablesource), [PrimaryExpression](#primaryexpression), [FunctionCall](#functioncall) *** ## FromSource ```sql theme={null} users ``` FromSource syntax diagram

**References:** [SubquerySource](#subquerysource), [TableSource](#tablesource), [TableValuedSource](#tablevaluedsource) [SelectStatement](#selectstatement), [JoinClause](#joinclause), [Subquery](#subquery), [CteDefinition](#ctedefinition) *** ## TableSource ```sql theme={null} users AS u ``` TableSource syntax diagram

**References:** [Identifier](#lexical-rules), [Reference](#reference) [FromSource](#fromsource) *** ## TableValuedCall ```sql theme={null} json_each(data) ``` TableValuedCall syntax diagram

**References:** [Expression](#expression), [Identifier](#lexical-rules) [TableValuedSource](#tablevaluedsource) *** ## TableValuedSource ```sql theme={null} json_each(data) AS items ``` TableValuedSource syntax diagram

**References:** [Identifier](#lexical-rules), [TableValuedCall](#tablevaluedcall) [FromSource](#fromsource) *** ## SubquerySource ```sql theme={null} (SELECT id FROM users) AS u ``` SubquerySource syntax diagram

**References:** [Identifier](#lexical-rules), [Subquery](#subquery) [FromSource](#fromsource) *** ## JoinClause ```sql theme={null} JOIN orders ON users.id = orders.user_id ``` JoinClause syntax diagram

**References:** [FromSource](#fromsource), [WhereClause](#whereclause) [SelectStatement](#selectstatement), [Subquery](#subquery), [CteDefinition](#ctedefinition) *** ## WhereClause ```sql theme={null} active = true AND age > 18 ``` WhereClause syntax diagram

**References:** [Condition](#condition) [SelectStatement](#selectstatement), [JoinClause](#joinclause), [Condition](#condition), [Subquery](#subquery), [CteDefinition](#ctedefinition) *** ## Condition ```sql theme={null} age BETWEEN 10 AND 100 ``` Condition syntax diagram

**References:** [Expression](#expression), [PredicateTail](#predicatetail), [WhereClause](#whereclause) [WhereClause](#whereclause), [CaseCondition](#casecondition) *** ## PredicateTail ```sql theme={null} IN (SELECT id FROM users) ``` PredicateTail syntax diagram

**References:** [Expression](#expression), [InSource](#insource) [Condition](#condition) *** ## InSource ```sql theme={null} (SELECT id FROM users) ``` InSource syntax diagram

**References:** [Expression](#expression), [Identifier](#lexical-rules), [Subquery](#subquery) [PredicateTail](#predicatetail) *** ## Expression ```sql theme={null} price * quantity + tax ``` Expression syntax diagram

### Operators Binary operators supported in scalar expressions, listed from highest to lowest precedence. PowerSync evaluates all binary operators with equal precedence (left to right). Use parentheses to control evaluation order. | Precedence | Operators | Description | | ---------- | ------------------ | --------------------------------- | | 1 | `\|\|` | String concatenation | | 2 | `*` `/` `%` | Multiplication, division, modulo | | 3 | `+` `-` | Addition, subtraction | | 4 | `&` `\|` `<<` `>>` | Bitwise AND, OR, left/right shift | | 5 | `<` `>` `<=` `>=` | Less than, greater than, etc. | | 6 | `=` `!=` | Equal, not equal | **References:** [PrimaryExpression](#primaryexpression), [PropertyAccess](#propertyaccess) [SelectItem](#selectitem), [TableValuedCall](#tablevaluedcall), [Condition](#condition), [PredicateTail](#predicatetail), [InSource](#insource), [PrimaryExpression](#primaryexpression), [SearchedCase](#searchedcase), [WhenClause](#whenclause), [SimpleCase](#simplecase), [WhenValueClause](#whenvalueclause), [CastExpression](#castexpression), [FunctionCall](#functioncall), [CteDefinition](#ctedefinition) *** ## PropertyAccess ```sql theme={null} ->'address'->>'city' ``` PropertyAccess syntax diagram

**References:** [IntegerLiteral](#lexical-rules), [StringLiteral](#lexical-rules) [Expression](#expression) *** ## PrimaryExpression ```sql theme={null} (price + tax) ``` PrimaryExpression syntax diagram

**References:** [CaseExpression](#caseexpression), [CastExpression](#castexpression), [Expression](#expression), [FunctionCall](#functioncall), [NumericLiteral](#lexical-rules), [Reference](#reference), [StringLiteral](#lexical-rules) [Expression](#expression) *** ## CaseExpression ```sql theme={null} CASE WHEN age >= 18 THEN 'adult' ELSE 'minor' END ``` CaseExpression syntax diagram

**References:** [SearchedCase](#searchedcase), [SimpleCase](#simplecase) [PrimaryExpression](#primaryexpression) *** ## SearchedCase ```sql theme={null} CASE WHEN x > 0 THEN 'positive' ELSE 'negative' END ``` SearchedCase syntax diagram

**References:** [Expression](#expression), [WhenClause](#whenclause) [CaseExpression](#caseexpression) *** ## WhenClause ```sql theme={null} WHEN age >= 18 THEN 'adult' ``` WhenClause syntax diagram

**References:** [CaseCondition](#casecondition), [Expression](#expression), [WhenClause](#whenclause) [SearchedCase](#searchedcase), [WhenClause](#whenclause) *** ## CaseCondition ```sql theme={null} x > 0 AND y IS NOT NULL ``` CaseCondition syntax diagram

**References:** [Condition](#condition) [WhenClause](#whenclause) *** ## SimpleCase ```sql theme={null} CASE status WHEN 1 THEN 'active' WHEN 0 THEN 'inactive' END ``` SimpleCase syntax diagram

**References:** [Expression](#expression), [WhenValueClause](#whenvalueclause) [CaseExpression](#caseexpression) *** ## WhenValueClause ```sql theme={null} WHEN 1 THEN 'active' ``` WhenValueClause syntax diagram

**References:** [Expression](#expression), [WhenValueClause](#whenvalueclause) [SimpleCase](#simplecase), [WhenValueClause](#whenvalueclause) *** ## CastExpression ```sql theme={null} CAST(age AS TEXT) ``` CastExpression syntax diagram

**References:** [Expression](#expression) [PrimaryExpression](#primaryexpression) *** ## FunctionCall ```sql theme={null} upper(name) ``` FunctionCall syntax diagram

**References:** [Expression](#expression), [Reference](#reference) [PrimaryExpression](#primaryexpression) *** ## Subquery ```sql theme={null} SELECT id FROM orders WHERE orders.user_id = users.id ``` Subquery syntax diagram

**References:** [FromSource](#fromsource), [JoinClause](#joinclause), [SelectItem](#selectitem), [WhereClause](#whereclause) [SubquerySource](#subquerysource), [InSource](#insource) *** ## CteDefinition ```sql theme={null} SELECT id, upper(name) AS display_name FROM users WHERE active = true ``` CteDefinition syntax diagram

**References:** [Expression](#expression), [FromSource](#fromsource), [Identifier](#lexical-rules), [JoinClause](#joinclause), [WhereClause](#whereclause) *** ## Lexical Rules | Token | Examples | Rule | | --------------------------------- | ------------------------------------------------------------------ | --------------------------------------- | | [Identifier](#identifier) | `user_id`, `MY_TABLE`, `"Column Name"`, `"with ""quotes"" inside"` | `[A-Z_] ([A-Z_0-9])*` | | [StringLiteral](#stringliteral) | `'hello'`, `'it''s'`, `''` | `"'" ([\x20-\x26] \| [\x28-\x7E])* "'"` | | [IntegerLiteral](#integerliteral) | `0`, `42`, `12345` | `([0-9])+` | | [NumericLiteral](#numericliteral) | `3.14`, `42`, `0.5` | `([0-9])+ ("." ([0-9])+)?` | ### Identifier Bare identifiers are normalized to lower case and may contain letters, digits, and underscores. Double-quoted identifiers ("name") allow any printable character and support escaped quotes (""). [SelectItem](#selectitem), [Reference](#reference), [TableSource](#tablesource), [TableValuedCall](#tablevaluedcall), [TableValuedSource](#tablevaluedsource), [SubquerySource](#subquerysource), [InSource](#insource), [CteDefinition](#ctedefinition) ### StringLiteral Single-quoted string literal. Embedded single quotes are escaped by doubling them (''). [PropertyAccess](#propertyaccess), [PrimaryExpression](#primaryexpression) ### IntegerLiteral One or more decimal digits (0-9). [PropertyAccess](#propertyaccess) ### NumericLiteral Decimal number: one or more digits with an optional fractional part (.digits). [PrimaryExpression](#primaryexpression)