fix(parser): model ALTER COLUMN nullability actions

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

@@ -41,6 +41,7 @@ public class AlterExpression implements Serializable {
     private String columnOldName;
     private List<ColumnDataType> colDataTypeList;
     private List<ColumnDropNotNull> columnDropNotNullList;
+    private List<ColumnSetNotNull> columnSetNotNullList;
     private List<ColumnDropDefault> columnDropDefaultList;
     private List<ColumnSetDefault> columnSetDefaultList;
     private List<ColumnSetVisibility> columnSetVisibilityList;
@@ -382,6 +383,13 @@ public void addColDropNotNull(ColumnDropNotNull columnDropNotNull) {
         columnDropNotNullList.add(columnDropNotNull);
     }
 
+    public void addColSetNotNull(ColumnSetNotNull columnSetNotNull) {
+        if (columnSetNotNullList == null) {
+            columnSetNotNullList = new ArrayList<>();
+        }
+        columnSetNotNullList.add(columnSetNotNull);
+    }
+
     public List<ColumnDropDefault> getColumnDropDefaultList() {
         return columnDropDefaultList;
     }
@@ -527,6 +535,10 @@ public List<ColumnDropNotNull> getColumnDropNotNullList() {
         return columnDropNotNullList;
     }
 
+    public List<ColumnSetNotNull> getColumnSetNotNullList() {
+        return columnSetNotNullList;
+    }
+
     public void addParameters(String... params) {
         if (parameters == null) {
             parameters = new ArrayList<>();
@@ -1134,6 +1146,9 @@ protected void toStringGeneral(StringBuilder b) {
             if (colDataTypeList.size() > 1) {
                 b.append(")");
             }
+        } else if (getColumnSetNotNullList() != null) {
+            b.append("COLUMN ");
+            b.append(PlainSelect.getStringList(columnSetNotNullList));
         } else if (getColumnDropNotNullList() != null) {
             b.append("COLUMN ");
             b.append(PlainSelect.getStringList(columnDropNotNullList));
@@ -1467,6 +1482,24 @@ public String toString() {
         }
     }
 
+    public static final class ColumnSetNotNull implements Serializable {
+
+        private final String columnName;
+
+        public ColumnSetNotNull(String columnName) {
+            this.columnName = columnName;
+        }
+
+        public String getColumnName() {
+            return columnName;
+        }
+
+        @Override
+        public String toString() {
+            return columnName + " SET NOT NULL";
+        }
+    }
+
     public static final class ColumnDropDefault implements Serializable {
 
         private final String columnName;

src/main/java/net/sf/jsqlparser/util/validation/validator/AlterValidator.java

@@ -17,6 +17,7 @@
 import net.sf.jsqlparser.statement.alter.AlterExpression;
 import net.sf.jsqlparser.statement.alter.AlterExpression.ColumnDataType;
 import net.sf.jsqlparser.statement.alter.AlterExpression.ColumnDropNotNull;
+import net.sf.jsqlparser.statement.alter.AlterExpression.ColumnSetNotNull;
 import net.sf.jsqlparser.statement.alter.AlterOperation;
 import net.sf.jsqlparser.util.validation.ValidationCapability;
 import net.sf.jsqlparser.util.validation.ValidationUtil;
@@ -47,6 +48,11 @@ public void validate(Alter alter, AlterExpression e) {
                         ColumnDropNotNull::getColumnName));
             }
 
+            if (e.getColumnSetNotNullList() != null) {
+                validateOptionalColumnNames(c, ValidationUtil.map(e.getColumnSetNotNullList(),
+                        ColumnSetNotNull::getColumnName));
+            }
+
             if (e.getColDataTypeList() != null) {
                 boolean validateForExist =
                         !EnumSet.of(AlterOperation.ADD).contains(e.getOperation());

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

@@ -12213,13 +12213,15 @@ Truncate Truncate():
 
 /**
  * Parses common column-level changes shared between the COLUMN-prefixed and bare forms:
- * DROP DEFAULT, SET DEFAULT, SET VISIBLE/INVISIBLE, and bracketed multi-column definitions.
+ * DROP DEFAULT, SET DEFAULT, SET NOT NULL, SET VISIBLE/INVISIBLE, and bracketed multi-column
+ * definitions.
  */
 void AlterExpressionColumnChanges(AlterExpression alterExp):
 {
     AlterExpression.ColumnDataType alterExpressionColumnDataType = null;
     AlterExpression.ColumnDropDefault alterExpressionColumnDropDefault = null;
     AlterExpression.ColumnSetDefault alterExpressionColumnSetDefault = null;
+    AlterExpression.ColumnSetNotNull alterExpressionColumnSetNotNull = null;
     AlterExpression.ColumnSetVisibility alterExpressionColumnSetVisibility = null;
 }
 {
@@ -12230,6 +12232,9 @@ void AlterExpressionColumnChanges(AlterExpression alterExp):
         LOOKAHEAD(3) alterExpressionColumnSetDefault = AlterExpressionColumnSetDefault()
             { alterExp.addColSetDefault(alterExpressionColumnSetDefault); }
         |
+        LOOKAHEAD(4) alterExpressionColumnSetNotNull = AlterExpressionColumnSetNotNull()
+            { alterExp.addColSetNotNull(alterExpressionColumnSetNotNull); }
+        |
         LOOKAHEAD(3) alterExpressionColumnSetVisibility = AlterExpressionColumnSetVisibility()
             { alterExp.addColSetVisibility(alterExpressionColumnSetVisibility); }
         |
@@ -12287,6 +12292,19 @@ AlterExpression.ColumnDropNotNull AlterExpressionColumnDropNotNull():
     }
 }
 
+AlterExpression.ColumnSetNotNull AlterExpressionColumnSetNotNull():
+{
+    String columnName = null;
+}
+{
+    columnName = RelObjectName()
+    <K_SET>
+    <K_NOT> <K_NULL>
+    {
+        return new AlterExpression.ColumnSetNotNull(columnName);
+    }
+}
+
 AlterExpression.ColumnDropDefault AlterExpressionColumnDropDefault():
 {
     String columnName = null;
@@ -12926,11 +12944,11 @@ AlterExpression AlterExpressionAddAlterModify():
             (
                 LOOKAHEAD(3) AlterExpressionColumnChanges(alterExp)
                 |
-                LOOKAHEAD(2) alterExpressionColumnDataType = AlterExpressionColumnDataType()
-                    { alterExp.addColDataType(alterExpressionColumnDataType); }
-                |
                 LOOKAHEAD(3) alterExpressionColumnDropNotNull = AlterExpressionColumnDropNotNull()
                     { alterExp.addColDropNotNull( alterExpressionColumnDropNotNull);}
+                |
+                LOOKAHEAD(2) alterExpressionColumnDataType = AlterExpressionColumnDataType()
+                    { alterExp.addColDataType(alterExpressionColumnDataType); }
             )
         )
         |

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

@@ -644,8 +644,23 @@ public void testAlterConstraintWithoutFKSourceColumnsIssue929() throws JSQLParse
 
     @Test
     public void testAlterTableAlterColumnDropNotNullIssue918() throws JSQLParserException {
-        assertSqlCanBeParsedAndDeparsed(
+        Alter alter = (Alter) assertSqlCanBeParsedAndDeparsed(
                 "ALTER TABLE \"user_table_t\" ALTER COLUMN name DROP NOT NULL");
+        AlterExpression expression = alter.getAlterExpressions().get(0);
+
+        assertNull(expression.getColDataTypeList());
+        assertEquals("name", expression.getColumnDropNotNullList().get(0).getColumnName());
+        assertTrue(expression.getColumnDropNotNullList().get(0).isWithNot());
+    }
+
+    @Test
+    public void testAlterTableAlterColumnSetNotNull() throws JSQLParserException {
+        Alter alter = (Alter) assertSqlCanBeParsedAndDeparsed(
+                "ALTER TABLE user_table ALTER COLUMN name SET NOT NULL");
+        AlterExpression expression = alter.getAlterExpressions().get(0);
+
+        assertNull(expression.getColDataTypeList());
+        assertEquals("name", expression.getColumnSetNotNullList().get(0).getColumnName());
     }
 
     @Test

src/test/java/net/sf/jsqlparser/statement/builder/ReflectionModelTest.java

@@ -141,6 +141,7 @@ public class ReflectionModelTest {
             new net.sf.jsqlparser.statement.alter.AlterExpression(),
             new net.sf.jsqlparser.statement.alter.AlterExpression.ColumnDataType(false),
             new net.sf.jsqlparser.statement.alter.AlterExpression.ColumnDropNotNull("name"),
+            new net.sf.jsqlparser.statement.alter.AlterExpression.ColumnSetNotNull("name"),
             new net.sf.jsqlparser.statement.merge.MergeInsert(),
             new net.sf.jsqlparser.statement.alter.DeferrableConstraint(),
             new net.sf.jsqlparser.statement.alter.EnableConstraint(),

src/test/java/net/sf/jsqlparser/util/validation/validator/AlterValidatorTest.java

@@ -151,4 +151,10 @@ public void testAlterTableAlterColumnDropNotNullIssue918() throws JSQLParserExce
                 DatabaseType.DATABASES);
     }
 
+    @Test
+    public void testAlterTableAlterColumnSetNotNull() throws JSQLParserException {
+        validateNoErrors("ALTER TABLE user_table ALTER COLUMN name SET NOT NULL", 1,
+                DatabaseType.DATABASES);
+    }
+
 }