diff --git a/src/auto-generator.ts b/src/auto-generator.ts
index f0d328ff..84b427fc 100644
--- a/src/auto-generator.ts
+++ b/src/auto-generator.ts
@@ -1,7 +1,7 @@
 import _ from "lodash";
 import { ColumnDescription } from "sequelize/types";
 import { DialectOptions, FKSpec } from "./dialects/dialect-options";
-import { AutoOptions, CaseFileOption, CaseOption, Field, IndexSpec, LangOption, qNameJoin, qNameSplit, recase, Relation, TableData, TSField, singularize, pluralize } from "./types";
+import { AutoOptions, CaseFileOption, CaseOption, Field, IndexSpec, LangOption, qNameJoin, qNameSplit, recase, Relation, TableData, TSField, singularize, pluralize, TypeOverrides, TableTypeOverride, ColumnTypeOverride, NullableFieldTypes } from "./types";
 
 /** Generates text from each table in TableData */
 export class AutoGenerator {
@@ -22,6 +22,7 @@ export class AutoGenerator {
     additional?: any;
     schema?: string;
     singularize: boolean;
+    typeOverrides?: TypeOverrides;
   };
 
   constructor(tableData: TableData, dialect: DialectOptions, options: AutoOptions) {
@@ -103,8 +104,19 @@ export class AutoGenerator {
           str += ` } from './${filename}';\n`;
         });
 
+        const typeOverrides = this.options.typeOverrides;
+        let tableTypeOverride: TableTypeOverride | undefined;
+        if (typeOverrides) {
+          if (typeOverrides.tables && tableNameOrig) {
+            tableTypeOverride = typeOverrides.tables[tableNameOrig];
+            if (tableTypeOverride) {
+              str += this.getTypeScriptTableOverrideImports(tableTypeOverride);
+            }
+          }
+        }
+
         str += "\nexport interface #TABLE#Attributes {\n";
-        str += this.addTypeScriptFields(table, true) + "}\n\n";
+        str += this.addTypeScriptFields(table, true, tableTypeOverride, typeOverrides?.nullableFieldType) + "}\n\n";
 
         const primaryKeys = this.getTypeScriptPrimaryKeys(table);
 
@@ -123,7 +135,7 @@ export class AutoGenerator {
         }
 
         str += "export class #TABLE# extends Model<#TABLE#Attributes, #TABLE#CreationAttributes> implements #TABLE#Attributes {\n";
-        str += this.addTypeScriptFields(table, false);
+        str += this.addTypeScriptFields(table, false, tableTypeOverride, typeOverrides?.nullableFieldType);
         str += "\n" + associations.str;
         str += "\n" + this.space[1] + "static initModel(sequelize: Sequelize.Sequelize): typeof " + tableName + " {\n";
         str += this.space[2] + tableName + ".init({\n";
@@ -546,7 +558,7 @@ export class AutoGenerator {
     const fields = _.keys(this.tables[table]);
     return fields.filter((field): boolean => {
       const fieldObj = this.tables[table][field];
-      return fieldObj.allowNull || (!!fieldObj.defaultValue || fieldObj.defaultValue === "") || fieldObj.primaryKey;
+      return fieldObj.allowNull || (!!fieldObj.defaultValue || fieldObj.defaultValue === "") || fieldObj.autoIncrement;
     });
   }
 
@@ -594,7 +606,7 @@ export class AutoGenerator {
             str += `${sp}${rel.childProp}!: ${rel.childModel};\n`;
             str += `${sp}get${pchild}!: Sequelize.HasOneGetAssociationMixin<${rel.childModel}>;\n`;
             str += `${sp}set${pchild}!: Sequelize.HasOneSetAssociationMixin<${rel.childModel}, ${rel.childModel}Id>;\n`;
-            str += `${sp}create${pchild}!: Sequelize.HasOneCreateAssociationMixin<${rel.childModel}CreationAttributes>;\n`;
+            str += `${sp}create${pchild}!: Sequelize.HasOneCreateAssociationMixin<${rel.childModel}>;\n`;
             needed[rel.childTable].add(rel.childModel);
             needed[rel.childTable].add(`${rel.childModel}Id`);
             needed[rel.childTable].add(`${rel.childModel}CreationAttributes`);
@@ -654,24 +666,93 @@ export class AutoGenerator {
     return { needed, str };
   }
 
-  private addTypeScriptFields(table: string, isInterface: boolean) {
+  private getTypeScriptTableOverrideImports(tableTypeOverride: TableTypeOverride) {
+    const columnTypeOverridesByType: { [type: string]: ColumnTypeOverride } = {}
+    // type should only be imported once for each file
+    _.keys(tableTypeOverride).forEach((columnName) => {
+      const columnTypeOverride = tableTypeOverride![columnName]!;
+      if (columnTypeOverride.type) {
+        columnTypeOverridesByType[columnTypeOverride.type] = columnTypeOverride;
+      }
+    });
+
+    // import per source
+    const imports: { [source: string]: { default?: string, types: string[] } } = {};
+    _.keys(columnTypeOverridesByType).forEach((type) => {
+      const columnTypeOverride = columnTypeOverridesByType[type];
+      if (columnTypeOverride.source) {
+        const importData = imports[columnTypeOverride.source];
+        if (importData) {
+          if (columnTypeOverride.isDefault) {
+            importData.default = type;
+          } else {
+            importData.types.push(type);
+          }
+        } else {
+          let newImportData: { default?: string, types: string[] };
+          if (columnTypeOverride.isDefault) {
+            newImportData = {
+              default: type,
+              types: [],
+            }
+          } else {
+            newImportData = {
+              types: [type],
+            }
+          }
+          imports[columnTypeOverride.source] = newImportData;
+        }
+      }
+    });
+
+    const importStrArr: string[] = [];
+    _.keys(imports).forEach((source) => {
+      const importData = imports[source];
+      let importStr = "import";
+      if (importData.default) {
+        importStr += ` ${importData.default}`;
+      }
+
+      if (importData.types.length !== 0) {
+        importStr += (importData.default ? ", " : " ") + `{ ${importData.types.join(", ")} }`;
+      }
+
+      importStr += ` from '${source}';`;
+      importStrArr.push(importStr);
+    });
+
+    if (importStrArr.length !== 0) {
+      return importStrArr.join("\n") + "\n";
+    }
+
+    return "";
+  }
+
+  private addTypeScriptFields(table: string, isInterface: boolean, tableTypeOverride: TableTypeOverride | undefined, nullableFieldType: NullableFieldTypes | undefined) {
     const sp = this.space[1];
     const fields = _.keys(this.tables[table]);
-    const notNull = isInterface ? '' : '!';
     let str = '';
+    const notOptional = isInterface ? '' : '!';
     fields.forEach(field => {
+      let columnTypeOverride: ColumnTypeOverride | undefined;
+      if (tableTypeOverride) {
+        columnTypeOverride = tableTypeOverride[field];
+      }
       const name = this.quoteName(recase(this.options.caseProp, field));
-      const isOptional = this.getTypeScriptFieldOptional(table, field);
-      str += `${sp}${name}${isOptional ? '?' : notNull}: ${this.getTypeScriptType(table, field)};\n`;
+      const fieldObj = this.tables[table][field];
+      let isOptional: boolean;
+      if (columnTypeOverride && columnTypeOverride.isOptional !== undefined) {
+        // override
+        isOptional = columnTypeOverride.isOptional;
+      } else {
+        isOptional = fieldObj.allowNull && nullableFieldType !== NullableFieldTypes.Null;
+      }
+      str += `${sp}${name}${isOptional ? '?' : notOptional}: ` +
+        `${columnTypeOverride && columnTypeOverride.type !== undefined ? columnTypeOverride.type : (this.getTypeScriptType(table, field) + (fieldObj.allowNull && nullableFieldType !== NullableFieldTypes.Optional ? " | null" : ""))};\n`;
     });
     return str;
   }
 
-  private getTypeScriptFieldOptional(table: string, field: string) {
-    const fieldObj = this.tables[table][field];
-    return fieldObj.allowNull;
-  }
-
   private getTypeScriptType(table: string, field: string) {
     const fieldObj = this.tables[table][field] as TSField;
     return this.getTypeScriptFieldType(fieldObj, "type");
diff --git a/src/types.ts b/src/types.ts
index 273acf2b..766d259c 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -172,6 +172,8 @@ export interface AutoOptions {
   storage?: string;
   /** Tables to export (default all) */
   tables?: string[];
+  /** Override the types of generated typescript file */
+  typeOverrides?: TypeOverrides;
   /** Database username */
   username?: string;
   /** Whether to export views (default false) */
@@ -221,3 +223,40 @@ export function recase(opt: CaseOption | CaseFileOption | undefined, val: string
   return val;
 }
 
+/**
+ * @type Optional. Name of the type
+ * @source Optional. File path of the type relative to file in the directory.
+ *         Leave undefined if overriding with primitive types
+ * @isDefault Optional. Whether the type is an export default. Default false
+ * @isOptional Optional. Override optionality
+ */
+export interface ColumnTypeOverride {
+  type?: string;
+  source?: string;
+  isDefault?: boolean;
+  isOptional?: boolean;
+}
+export type TableTypeOverride = { [columnName: string]: ColumnTypeOverride | undefined };
+export type TableTypeOverrides = { [tableName: string]: TableTypeOverride | undefined }
+
+export enum NullableFieldTypes {
+  Null = "NULL",
+  Optional = "OPTIONAL",
+  NullAndOptional = "NULL_AND_OPTIONAL"
+}
+
+/**
+ * @tables {
+ *  roles: {
+ *   name: {
+ *     type: "RoleTypes",
+ *     source: "../RoleTypes"
+ *   }
+ *  }
+ * }
+ * @nullableFieldType use "NULL", "OPTIONAL", OR "NULL_AND_OPTIONAL" for nullable table columns. Default "NULL_AND_OPTIONAL"
+ */
+export interface TypeOverrides {
+  tables?: TableTypeOverrides;
+  nullableFieldType?: NullableFieldTypes;
+}