fix: parse every MySQL character set form of ALTER TABLE CONVERT TO

src/main/java/net/sf/jsqlparser/statement/alter/AlterExpression.java

@@ -72,6 +72,7 @@ public enum TableRenameKeyword {
     private List<String> parameters;
 
     private ConvertType convertType;
+    private boolean useCharsetKeyword;
     private boolean hasEqualForCharacterSet;
     private boolean hasEqualForCollate;
 
@@ -956,6 +957,15 @@ public void setConvertType(ConvertType convertType) {
         this.convertType = convertType;
     }
 
+    /** Whether the character set clause uses MySQL's CHARSET abbreviation. */
+    public boolean isUseCharsetKeyword() {
+        return useCharsetKeyword;
+    }
+
+    public void setUseCharsetKeyword(boolean useCharsetKeyword) {
+        this.useCharsetKeyword = useCharsetKeyword;
+    }
+
     public String getCharacterSet() {
         return characterSet;
     }
@@ -1485,15 +1495,16 @@ protected void toStringDropSpecial(StringBuilder b) {
 
     protected void toStringConvert(StringBuilder b) {
         if (operation == AlterOperation.CONVERT) {
+            String keyword = useCharsetKeyword ? "CHARSET " : "CHARACTER SET ";
             if (convertType == ConvertType.CONVERT_TO) {
-                b.append("CONVERT TO CHARACTER SET ");
+                b.append("CONVERT TO ").append(keyword);
             } else if (convertType == ConvertType.DEFAULT_CHARACTER_SET) {
-                b.append("DEFAULT CHARACTER SET ");
+                b.append("DEFAULT ").append(keyword);
                 if (hasEqualForCharacterSet) {
                     b.append("= ");
                 }
             } else if (convertType == ConvertType.CHARACTER_SET) {
-                b.append("CHARACTER SET ");
+                b.append(keyword);
                 if (hasEqualForCharacterSet) {
                     b.append("= ");
                 }

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -19131,6 +19131,7 @@ AlterExpression AlterSharedTableOption():
                 charset.setConvertType(useDefault ? AlterExpression.ConvertType.DEFAULT_CHARACTER_SET
                         : AlterExpression.ConvertType.CHARACTER_SET);
                 charset.setCharacterSet(option.getValue());
+                charset.setUseCharsetKeyword(option.getName().toUpperCase(Locale.ROOT).endsWith("CHARSET"));
                 charset.setHasEqualForCharacterSet(option.isUseEquals());
                 if (collation != null) {
                     charset.setCollation(collation.getValue());
@@ -19519,10 +19520,18 @@ void TypeCharacterSet(ColDataType type):
 {
     ( <K_CHARACTER> <K_SET>
       | LOOKAHEAD({ isKeywordAhead("CHARSET") }) <S_IDENTIFIER> { abbreviated = true; } )
-    ( name=<S_IDENTIFIER> | name=<K_BINARY> | name=<S_CHAR_LITERAL> | name=<S_QUOTED_IDENTIFIER> )
+    name=CharacterSetName()
     { type.setCharacterSet(name.image); type.setUseCharsetKeyword(abbreviated); }
 }
 
+/** A MySQL character set or collation name: an identifier, BINARY or a quoted name. */
+Token CharacterSetName():
+{ Token name; }
+{
+    ( name=<S_IDENTIFIER> | name=<K_BINARY> | name=<S_CHAR_LITERAL> | name=<S_QUOTED_IDENTIFIER> )
+    { return name; }
+}
+
 XmlTypeModifier XmlTypeModifier():
 {
     XmlTypeModifier.Kind kind = null;
@@ -22081,8 +22090,11 @@ AlterExpression AlterExpression():
           alterExp.setOperation(AlterOperation.CONVERT);
           alterExp.setConvertType(AlterExpression.ConvertType.CONVERT_TO);
         }
-        <K_TO> <K_CHARACTER> <K_SET> tk=<S_IDENTIFIER> { alterExp.setCharacterSet(tk.image); }
-        [ LOOKAHEAD(2) <K_COLLATE> tk2=<S_IDENTIFIER> { alterExp.setCollation(tk2.image); }]
+        <K_TO>
+        ( <K_CHARACTER> <K_SET>
+          | LOOKAHEAD({ isKeywordAhead("CHARSET") }) <S_IDENTIFIER> { alterExp.setUseCharsetKeyword(true); } )
+        ( tk=<K_DEFAULT> | tk=CharacterSetName() ) { alterExp.setCharacterSet(tk.image); }
+        [ LOOKAHEAD(2) <K_COLLATE> tk2=CharacterSetName() { alterExp.setCollation(tk2.image); }]
         )
       |
         alterExp = AlterExpressionDiscardOrImport()

src/test/java/net/sf/jsqlparser/statement/alter/MySqlConvertToCharacterSetTest.java

@@ -0,0 +1,96 @@
+/*-
+ * #%L
+ * JSQLParser library
+ * %%
+ * Copyright (C) 2004 - 2026 JSQLParser
+ * %%
+ * Dual licensed under GNU LGPL 2.1 or Apache License 2.0
+ * #L%
+ */
+package net.sf.jsqlparser.statement.alter;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.function.Consumer;
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.parser.AbstractJSqlParser.Dialect;
+import net.sf.jsqlparser.parser.CCJSqlParser;
+import net.sf.jsqlparser.parser.CCJSqlParserUtil;
+import net.sf.jsqlparser.statement.Statement;
+import net.sf.jsqlparser.util.deparser.StatementDeParser;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class MySqlConvertToCharacterSetTest {
+    private static final Consumer<CCJSqlParser> MYSQL = p -> p.withDialect(Dialect.MYSQL);
+
+    @ParameterizedTest
+    @ValueSource(strings = {"ALTER TABLE t CONVERT TO CHARSET utf8mb4",
+            "ALTER TABLE t CONVERT TO CHARSET utf8mb4 COLLATE utf8mb4_bin",
+            "ALTER TABLE t CONVERT TO CHARACTER SET DEFAULT",
+            "ALTER TABLE t CONVERT TO CHARACTER SET DEFAULT COLLATE utf8mb4_bin",
+            "ALTER TABLE t CONVERT TO CHARACTER SET binary",
+            "ALTER TABLE t CONVERT TO CHARACTER SET binary COLLATE binary",
+            "ALTER TABLE t CONVERT TO CHARACTER SET 'utf8mb4'",
+            "ALTER TABLE t CONVERT TO CHARACTER SET utf8mb4 COLLATE 'utf8mb4_bin'",
+            "ALTER TABLE t CONVERT TO CHARACTER SET `utf8mb4` COLLATE `utf8mb4_bin`",
+            "ALTER TABLE t CONVERT TO CHARSET utf8mb4, ADD COLUMN c INT",
+            "ALTER TABLE t DEFAULT CHARSET utf8mb4",
+            "ALTER TABLE t CHARSET = utf8mb4 COLLATE = utf8mb4_bin"})
+    void keepsEveryCharacterSetForm(String sql) throws JSQLParserException {
+        for (Statement statement : new Statement[] {CCJSqlParserUtil.parse(sql),
+                CCJSqlParserUtil.parse(sql, MYSQL)}) {
+            assertEquals(sql, statement.toString());
+            StringBuilder deparsed = new StringBuilder();
+            statement.accept(new StatementDeParser(deparsed));
+            assertEquals(sql, deparsed.toString());
+        }
+        assertEquals(2, CCJSqlParserUtil.parseStatements(sql + "; SELECT 1", MYSQL).size());
+    }
+
+    @Test
+    void exposesCharsetSpellingNameAndCollation() throws JSQLParserException {
+        AlterExpression action =
+                parseAction("ALTER TABLE t CONVERT TO CHARSET utf8mb4 COLLATE 'utf8mb4_bin'");
+        assertEquals(AlterOperation.CONVERT, action.getOperation());
+        assertEquals(AlterExpression.ConvertType.CONVERT_TO, action.getConvertType());
+        assertTrue(action.isUseCharsetKeyword());
+        assertEquals("utf8mb4", action.getCharacterSet());
+        assertEquals("'utf8mb4_bin'", action.getCollation());
+
+        action.setUseCharsetKeyword(false);
+        action.setCollation("utf8mb4_0900_ai_ci");
+        assertEquals("CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci",
+                action.toString());
+
+        AlterExpression standard = parseAction("ALTER TABLE t CONVERT TO CHARACTER SET DEFAULT");
+        assertFalse(standard.isUseCharsetKeyword());
+        assertEquals("DEFAULT", standard.getCharacterSet());
+        assertNull(standard.getCollation());
+    }
+
+    @Test
+    void keepsCharsetSpellingOfTableOptions() throws JSQLParserException {
+        AlterExpression action = parseAction("ALTER TABLE t DEFAULT CHARSET = utf8mb4");
+        assertEquals(AlterExpression.ConvertType.DEFAULT_CHARACTER_SET, action.getConvertType());
+        assertTrue(action.isUseCharsetKeyword());
+        assertFalse(
+                parseAction("ALTER TABLE t DEFAULT CHARACTER SET = utf8mb4").isUseCharsetKeyword());
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"ALTER TABLE t CONVERT TO CHARSET",
+            "ALTER TABLE t CONVERT TO utf8mb4",
+            "ALTER TABLE t CONVERT TO CHARSET = utf8mb4",
+            "ALTER TABLE t CONVERT TO CHARACTER SET utf8mb4 COLLATE"})
+    void rejectsIncompleteForms(String sql) {
+        assertThrows(JSQLParserException.class, () -> CCJSqlParserUtil.parse(sql, MYSQL));
+    }
+
+    private static AlterExpression parseAction(String sql) throws JSQLParserException {
+        Alter alter = (Alter) CCJSqlParserUtil.parse(sql, MYSQL);
+        assertEquals(1, alter.getAlterExpressions().size());
+        return alter.getAlterExpressions().get(0);
+    }
+}