Document ALTER TABLE ALTER COLUMN DROP NOT NULL and remove incorrect information

h2/src/docsrc/help/help.csv

@@ -357,8 +357,8 @@ ALTER TABLE [ IF EXISTS ] tableName ALTER COLUMN columnName
     | { SET DEFAULT expression }
     | { DROP DEFAULT }
     | { SET ON UPDATE expression }
-    | { SET NULL }
     | { SET NOT NULL }
+    | { DROP NOT NULL } | { SET NULL }
     | { SET { VISIBLE | INVISIBLE } }
     | { DROP ON UPDATE } }
 ","
@@ -382,11 +382,10 @@ DROP DEFAULT removes the default value of a column.
 
 SET ON UPDATE changes the value that is set on update if value for this column is not specified in update statement.
 
-SET NULL sets a column to allow NULL. The row may not be part of a primary key.
-Single column indexes on this column are dropped.
-
 SET NOT NULL sets a column to not allow NULL. Rows may not contains NULL in this column.
 
+DROP NOT NULL and SET NULL set a column to allow NULL. The row may not be part of a primary key.
+
 SET INVISIBLE makes the column hidden, i.e. it will not appear in SELECT * results.
 SET VISIBLE has the reverse effect.
 

h2/src/main/org/h2/command/CommandInterface.java

@@ -63,9 +63,9 @@ public interface CommandInterface {
     int ALTER_TABLE_ALTER_COLUMN_NOT_NULL = 8;
 
     /**
-     * The type of a ALTER TABLE ALTER COLUMN SET NULL statement.
+     * The type of a ALTER TABLE ALTER COLUMN DROP NOT NULL statement.
      */
-    int ALTER_TABLE_ALTER_COLUMN_NULL = 9;
+    int ALTER_TABLE_ALTER_COLUMN_DROP_NOT_NULL = 9;
 
     /**
      * The type of a ALTER TABLE ALTER COLUMN SET DEFAULT and ALTER TABLE ALTER

h2/src/main/org/h2/command/Parser.java

@@ -7216,7 +7216,7 @@ public class Parser {
                 Column column = columnIfTableExists(schema, tableName, columnName, ifTableExists);
                 command.setOldColumn(column);
                 if (nullConstraint == NullConstraintType.NULL_IS_ALLOWED) {
-                    command.setType(CommandInterface.ALTER_TABLE_ALTER_COLUMN_NULL);
+                    command.setType(CommandInterface.ALTER_TABLE_ALTER_COLUMN_DROP_NOT_NULL);
                 } else {
                     command.setType(CommandInterface.ALTER_TABLE_ALTER_COLUMN_NOT_NULL);
                 }
@@ -7273,7 +7273,7 @@ public class Parser {
                 command.setTableName(tableName);
                 command.setIfTableExists(ifTableExists);
                 command.setOldColumn(column);
-                command.setType(CommandInterface.ALTER_TABLE_ALTER_COLUMN_NULL);
+                command.setType(CommandInterface.ALTER_TABLE_ALTER_COLUMN_DROP_NOT_NULL);
                 return command;
             } else if (readIf("TYPE")) {
                 // PostgreSQL compatibility
@@ -7294,7 +7294,7 @@ public class Parser {
                 NullConstraintType nullConstraint = parseNotNullConstraint();
                 switch (nullConstraint) {
                 case NULL_IS_ALLOWED:
-                    command.setType(CommandInterface.ALTER_TABLE_ALTER_COLUMN_NULL);
+                    command.setType(CommandInterface.ALTER_TABLE_ALTER_COLUMN_DROP_NOT_NULL);
                     break;
                 case NULL_IS_NOT_ALLOWED:
                     command.setType(CommandInterface.ALTER_TABLE_ALTER_COLUMN_NOT_NULL);

h2/src/main/org/h2/command/ddl/AlterTableAlterColumn.java

@@ -137,7 +137,7 @@ public class AlterTableAlterColumn extends CommandWithColumns {
             db.updateMeta(session, table);
             break;
         }
-        case CommandInterface.ALTER_TABLE_ALTER_COLUMN_NULL: {
+        case CommandInterface.ALTER_TABLE_ALTER_COLUMN_DROP_NOT_NULL: {
             if (oldColumn.isNullable()) {
                 // no change
                 break;

h2/src/test/org/h2/test/scripts/ddl/alterTableAlterColumn.sql

@@ -23,5 +23,29 @@ ALTER TABLE TEST ALTER COLUMN T DROP DEFAULT;
 SELECT COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMN_NAME = 'T';
 >> INT
 
+-- SET NOT NULL
+ALTER TABLE TEST ALTER COLUMN T SET NOT NULL;
+> ok
+
+SELECT COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMN_NAME = 'T';
+>> INT NOT NULL
+
+-- DROP NOT NULL
+ALTER TABLE TEST ALTER COLUMN T DROP NOT NULL;
+> ok
+
+SELECT COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMN_NAME = 'T';
+>> INT
+
+ALTER TABLE TEST ALTER COLUMN T SET NOT NULL;
+> ok
+
+-- SET NULL
+ALTER TABLE TEST ALTER COLUMN T SET NULL;
+> ok
+
+SELECT COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMN_NAME = 'T';
+>> INT
+
 DROP TABLE TEST;
 > ok