Merge pull request #150 from Jacyking/master

readme 作为第三方库引入

README.md

@@ -192,6 +192,55 @@ int main() {
 cmake -B build -DENABLE_SQLITE3=ON -DCMAKE_BUILD_TYPE=Debug
 cmake --build build --config Debug
 
+## 作为第三方库引入
+
+mysql
+```cmake
+set(ENABLE_MYSQL ON)
+add_definitions(-DORMPP_ENABLE_MYSQL)
+add_subdirectory(ormpp)
+```
+或者
+```cmake
+set(ENABLE_MYSQL ON)
+add_definitions(-DORMPP_ENABLE_MYSQL)
+add_library(ormpp INTERFACE)
+include(cmake/mysql.cmake)
+target_link_libraries(ormpp INTERFACE ${MYSQL_LIBRARY})
+target_include_directories(ormpp INTERFACE ormpp ormpp/ormpp ${MYSQL_INCLUDE_DIR})
+```
+
+sqlite
+```cmake
+set(ENABLE_SQLITE3 ON)
+add_definitions(-DORMPP_ENABLE_SQLITE3)
+add_subdirectory(ormpp)
+```
+或者
+```cmake
+set(ENABLE_SQLITE3 ON)
+add_definitions(-DORMPP_ENABLE_SQLITE3)
+add_library(ormpp INTERFACE)
+target_link_libraries(ormpp INTERFACE sqlite3)
+target_include_directories(ormpp INTERFACE ormpp ormpp/ormpp thirdparty/sqlite3)
+```
+
+pg
+```cmake
+set(ENABLE_PG ON)
+add_definitions(-DORMPP_ENABLE_PG)
+add_subdirectory(ormpp)
+```
+或者
+```cmake
+set(ENABLE_PG ON)
+add_definitions(-DORMPP_ENABLE_PG)
+add_library(ormpp INTERFACE)
+include(cmake/pgsql.cmake)
+target_link_libraries(ormpp INTERFACE ${PGSQL_LIBRARY})
+target_include_directories(ormpp INTERFACE ormpp ormpp/ormpp ${PGSQL_INCLUDE_DIR})
+```
+
 ### 编译器支持
 
 需要支持C++17的编译器, 要求的编译器版本：linux gcc7.2, clang4.0; windows >vs2017 update5