liquibase-core/src/main/java/liquibase/sqlgenerator/core/InsertOrUpdateGeneratorInformix.java
private String convertToString(Object newValue, Database database) {
    String sqlString;
    if (newValue == null || newValue.toString().equals("") || newValue.toString().equalsIgnoreCase("NULL")) {
      sqlString = "NULL::INTEGER";
    } else if (newValue instanceof String && !looksLikeFunctionCall(((String) newValue), database)) {
      sqlString = "'" + database.escapeStringForDatabase(newValue.toString()) + "'";
    } else if (newValue instanceof Date) {
      sqlString = database.getDateLiteral(((Date) newValue));
    } else if (newValue instanceof Boolean) {
      if (((Boolean) newValue)) {
        sqlString = DataTypeFactory.getInstance().getTrueBooleanValue(database);
      } else {
        sqlString = DataTypeFactory.getInstance().getFalseBooleanValue(database);
      }
    } else {
      sqlString = newValue.toString();
    }
    return sqlString;
  }
private String convertToString(Object newValue, Database database) {
    String sqlString;
    if (newValue == null || newValue.toString().equals("") || newValue.toString().equalsIgnoreCase("NULL")) {
      sqlString = "NULL::INTEGER";
    } else if (newValue instanceof String && !looksLikeFunctionCall(((String) newValue), database)) {
      sqlString = "'" + database.escapeStringForDatabase(newValue.toString()) + "'";
    } else if (newValue instanceof Date) {
      sqlString = database.getDateLiteral(((Date) newValue));
    } else if (newValue instanceof Boolean) {
      if (((Boolean) newValue)) {
        sqlString = DataTypeFactory.getInstance().getTrueBooleanValue(database);
      } else {
        sqlString = DataTypeFactory.getInstance().getFalseBooleanValue(database);
      }
    } else {
      sqlString = newValue.toString();
    }
    return sqlString;
  }
Copied and modified from liquibase.sqlgenerator.core.InsertOrUpdateGeneratorMySQL