feat: SQL 语法支持 CREATE TABLE IF NOT EXISTS

- Parser 支持 CREATE TABLE IF NOT EXISTS 语法
- AST CreateTableStatement 新增 ifNotExists 字段
- Executor 表已存在时静默跳过
- 修复 demo.html Aria 预设报错

dist/metona-sqlark.cjs.js

@@ -4001,6 +4001,12 @@ class QueryExecutor {
         return this.engine.delete(plan.table, plan);
     }
     async executeCreateTable(stmt) {
+        // IF NOT EXISTS: 表已存在时静默返回
+        if (stmt.ifNotExists) {
+            const exists = await this.engine.hasTable(stmt.name);
+            if (exists)
+                return;
+        }
         const columns = {};
         for (const col of stmt.columns)
             columns[col.name] = astColumnToColumnDef(col);
@@ -4763,6 +4769,14 @@ class Parser {
     parseCreateTable() {
         this.expect(TokenType.CREATE);
         this.expect(TokenType.TABLE);
+        // IF NOT EXISTS（可选）
+        let ifNotExists = false;
+        if (this.curTokenIs(TokenType.IF)) {
+            this.nextToken();
+            this.expect(TokenType.NOT);
+            this.expect(TokenType.EXISTS);
+            ifNotExists = true;
+        }
         const tableName = this.expectIdentifier('table name');
         this.expect(TokenType.LPAREN);
         const columns = [];
@@ -4772,7 +4786,7 @@ class Parser {
             columns.push(this.parseColumnDef());
         } while (this.curTokenIs(TokenType.COMMA));
         this.expect(TokenType.RPAREN);
-        return { type: 'CREATE_TABLE', name: tableName, columns };
+        return { type: 'CREATE_TABLE', name: tableName, columns, ifNotExists: ifNotExists || undefined };
     }
     parseColumnDef() {
         const name = this.expectIdentifier('column name');

dist/metona-sqlark.d.ts

@@ -224,6 +224,8 @@ interface CreateTableStatement {
     type: 'CREATE_TABLE';
     name: string;
     columns: ASTColumnDef[];
+    /** IF NOT EXISTS — 表已存在时不报错 */
+    ifNotExists?: boolean;
 }
 interface DropTableStatement {
     type: 'DROP_TABLE';

dist/metona-sqlark.esm.js

@@ -3997,6 +3997,12 @@ class QueryExecutor {
         return this.engine.delete(plan.table, plan);
     }
     async executeCreateTable(stmt) {
+        // IF NOT EXISTS: 表已存在时静默返回
+        if (stmt.ifNotExists) {
+            const exists = await this.engine.hasTable(stmt.name);
+            if (exists)
+                return;
+        }
         const columns = {};
         for (const col of stmt.columns)
             columns[col.name] = astColumnToColumnDef(col);
@@ -4759,6 +4765,14 @@ class Parser {
     parseCreateTable() {
         this.expect(TokenType.CREATE);
         this.expect(TokenType.TABLE);
+        // IF NOT EXISTS（可选）
+        let ifNotExists = false;
+        if (this.curTokenIs(TokenType.IF)) {
+            this.nextToken();
+            this.expect(TokenType.NOT);
+            this.expect(TokenType.EXISTS);
+            ifNotExists = true;
+        }
         const tableName = this.expectIdentifier('table name');
         this.expect(TokenType.LPAREN);
         const columns = [];
@@ -4768,7 +4782,7 @@ class Parser {
             columns.push(this.parseColumnDef());
         } while (this.curTokenIs(TokenType.COMMA));
         this.expect(TokenType.RPAREN);
-        return { type: 'CREATE_TABLE', name: tableName, columns };
+        return { type: 'CREATE_TABLE', name: tableName, columns, ifNotExists: ifNotExists || undefined };
     }
     parseColumnDef() {
         const name = this.expectIdentifier('column name');

dist/metona-sqlark.js

@@ -4003,6 +4003,12 @@
             return this.engine.delete(plan.table, plan);
         }
         async executeCreateTable(stmt) {
+            // IF NOT EXISTS: 表已存在时静默返回
+            if (stmt.ifNotExists) {
+                const exists = await this.engine.hasTable(stmt.name);
+                if (exists)
+                    return;
+            }
             const columns = {};
             for (const col of stmt.columns)
                 columns[col.name] = astColumnToColumnDef(col);
@@ -4765,6 +4771,14 @@
         parseCreateTable() {
             this.expect(TokenType.CREATE);
             this.expect(TokenType.TABLE);
+            // IF NOT EXISTS（可选）
+            let ifNotExists = false;
+            if (this.curTokenIs(TokenType.IF)) {
+                this.nextToken();
+                this.expect(TokenType.NOT);
+                this.expect(TokenType.EXISTS);
+                ifNotExists = true;
+            }
             const tableName = this.expectIdentifier('table name');
             this.expect(TokenType.LPAREN);
             const columns = [];
@@ -4774,7 +4788,7 @@
                 columns.push(this.parseColumnDef());
             } while (this.curTokenIs(TokenType.COMMA));
             this.expect(TokenType.RPAREN);
-            return { type: 'CREATE_TABLE', name: tableName, columns };
+            return { type: 'CREATE_TABLE', name: tableName, columns, ifNotExists: ifNotExists || undefined };
         }
         parseColumnDef() {
             const name = this.expectIdentifier('column name');