diff --git a/backend-spring/build.gradle b/backend-spring/build.gradle
index 457ea85b..65b211d0 100644
--- a/backend-spring/build.gradle
+++ b/backend-spring/build.gradle
@@ -33,6 +33,11 @@ dependencies {
     runtimeOnly 'io.jsonwebtoken:jjwt-impl:0.12.3'
     runtimeOnly 'io.jsonwebtoken:jjwt-jackson:0.12.3'
     implementation 'org.postgresql:postgresql'
+    // 외부 커넥션 테스트용 JDBC 드라이버 (runtimeOnly — 내부 비즈니스 DB 는 PostgreSQL 만 사용)
+    runtimeOnly 'org.mariadb.jdbc:mariadb-java-client:3.4.1'
+    runtimeOnly 'com.mysql:mysql-connector-j:8.4.0'
+    runtimeOnly 'com.microsoft.sqlserver:mssql-jdbc:12.8.1.jre11'
+    runtimeOnly 'org.xerial:sqlite-jdbc:3.46.1.0'
     compileOnly 'org.projectlombok:lombok'
     annotationProcessor 'org.projectlombok:lombok'
     implementation 'org.flywaydb:flyway-core'
diff --git a/backend-spring/src/main/java/com/erp/provisioning/DataCopier.java b/backend-spring/src/main/java/com/erp/provisioning/DataCopier.java
index 165b56be..1d772e20 100644
--- a/backend-spring/src/main/java/com/erp/provisioning/DataCopier.java
+++ b/backend-spring/src/main/java/com/erp/provisioning/DataCopier.java
@@ -100,13 +100,22 @@ public class DataCopier {
         try (Statement us = dst.createStatement()) {
             for (String[] r : rows) {
                 String seq = r[0], tbl = r[1], col = r[2], coltype = r[3];
-                if (!isIntegerLike(coltype)) {
+                String sql;
+                if (isIntegerLike(coltype)) {
+                    sql = String.format(
+                            "SELECT setval('%s', GREATEST(COALESCE((SELECT MAX(\"%s\") FROM \"%s\"), 0), 1))",
+                            seq.replace("'", "''"), col, tbl);
+                } else if (isVarcharLike(coltype)) {
+                    // V001 마이그레이션으로 INT → VARCHAR 로 바뀐 PK 컬럼도 시퀀스가 연결되어 있고,
+                    // INSERT 시 DEFAULT nextval 이 호출되므로 max 재설정 필요. 비숫자 PK(UUID 등) 가
+                    // 섞여 있어도 정규식으로 거르고 숫자 PK 만 max 계산.
+                    sql = String.format(
+                            "SELECT setval('%s', GREATEST(COALESCE((SELECT MAX(\"%s\"::bigint) FROM \"%s\" WHERE \"%s\" ~ '^[0-9]+$'), 0), 1))",
+                            seq.replace("'", "''"), col, tbl, col);
+                } else {
                     skippedType++;
                     continue;
                 }
-                String sql = String.format(
-                        "SELECT setval('%s', GREATEST(COALESCE((SELECT MAX(\"%s\") FROM \"%s\"), 0), 1))",
-                        seq.replace("'", "''"), col, tbl);
                 try {
                     us.execute(sql);
                     updated++;
@@ -117,14 +126,8 @@ public class DataCopier {
                 }
             }
         }
-        // invyone 은 대다수 PK 가 VARCHAR (문자열 PK). 시퀀스가 연결되어 있어도 실제 INSERT 때
-        // nextval 을 사용하지 않으므로 setval 은 no-op. skipped_non_integer 값이 높아도 정상.
-        if (updated == 0 && skippedErr == 0) {
-            log.info("[Provisioning] RESET SEQUENCES: skipped all {} (string-PK schema, no-op)", rows.size());
-        } else {
-            log.info("[Provisioning] RESET SEQUENCES: updated={} skipped_non_integer={} skipped_error={} total={}",
-                    updated, skippedType, skippedErr, rows.size());
-        }
+        log.info("[Provisioning] RESET SEQUENCES: updated={} skipped_non_numeric={} skipped_error={} total={}",
+                updated, skippedType, skippedErr, rows.size());
         return updated;
     }
 
@@ -135,6 +138,12 @@ public class DataCopier {
                 || t.startsWith("int4") || t.startsWith("int8") || t.startsWith("int2");
     }
 
+    private static boolean isVarcharLike(String coltype) {
+        if (coltype == null) return false;
+        String t = coltype.toLowerCase();
+        return t.startsWith("character varying") || t.startsWith("varchar") || t.startsWith("text");
+    }
+
     private List<String> listColumns(Connection conn, String table) throws SQLException {
         List<String> cols = new ArrayList<>();
         try (PreparedStatement ps = conn.prepareStatement(
diff --git a/backend-spring/src/main/java/com/erp/service/ExternalDbConnectionService.java b/backend-spring/src/main/java/com/erp/service/ExternalDbConnectionService.java
index ef319b94..f81fe993 100644
--- a/backend-spring/src/main/java/com/erp/service/ExternalDbConnectionService.java
+++ b/backend-spring/src/main/java/com/erp/service/ExternalDbConnectionService.java
@@ -297,29 +297,61 @@ public class ExternalDbConnectionService extends BaseService {
     private Map<String, Object> executeConnectionTest(
             String dbType, Map<String, Object> conn, String password) {
 
+        String type = dbType == null ? "" : dbType.toLowerCase();
         String host = str(conn, "host");
-        int port = toInt(conn, "port", 5432);
+        int port = toInt(conn, "port", defaultPort(type));
         String database = str(conn, "database_name");
         String username = str(conn, "username");
         String sslEnabled = str(conn, "ssl_enabled");
         int connTimeout = toInt(conn, "connection_timeout", 30);
+        boolean ssl = "Y".equalsIgnoreCase(sslEnabled);
 
-        if (!"postgresql".equalsIgnoreCase(dbType)) {
-            Map<String, Object> result = new LinkedHashMap<>();
-            result.put("success", false);
-            result.put("message", "이 버전에서는 PostgreSQL 연결만 테스트가 지원됩니다.");
-            return result;
-        }
-
-        String url = String.format("jdbc:postgresql://%s:%d/%s", host, port, database);
+        String url;
         Properties props = new Properties();
-        props.setProperty("user", username);
-        props.setProperty("password", password);
-        props.setProperty("connect_timeout", String.valueOf(connTimeout));
-        props.setProperty("socket_timeout", "30");
-        if ("Y".equalsIgnoreCase(sslEnabled)) {
-            props.setProperty("ssl", "true");
-            props.setProperty("sslmode", "require");
+        if (username != null) props.setProperty("user", username);
+        if (password != null) props.setProperty("password", password);
+
+        switch (type) {
+            case "postgresql" -> {
+                url = String.format("jdbc:postgresql://%s:%d/%s", host, port, database);
+                props.setProperty("connect_timeout", String.valueOf(connTimeout));
+                props.setProperty("socket_timeout", "30");
+                if (ssl) {
+                    props.setProperty("ssl", "true");
+                    props.setProperty("sslmode", "require");
+                }
+            }
+            case "mysql" -> {
+                url = String.format("jdbc:mysql://%s:%d/%s", host, port, database);
+                props.setProperty("connectTimeout", String.valueOf(connTimeout * 1000));
+                props.setProperty("socketTimeout", "30000");
+                props.setProperty("useSSL", String.valueOf(ssl));
+                props.setProperty("allowPublicKeyRetrieval", "true");
+            }
+            case "mariadb" -> {
+                url = String.format("jdbc:mariadb://%s:%d/%s", host, port, database);
+                props.setProperty("connectTimeout", String.valueOf(connTimeout * 1000));
+                props.setProperty("socketTimeout", "30000");
+                if (ssl) props.setProperty("useSsl", "true");
+            }
+            case "mssql", "sqlserver" -> {
+                StringBuilder sb = new StringBuilder()
+                    .append("jdbc:sqlserver://").append(host).append(':').append(port)
+                    .append(";databaseName=").append(database)
+                    .append(";loginTimeout=").append(connTimeout)
+                    .append(";encrypt=").append(ssl ? "true;trustServerCertificate=true" : "false");
+                url = sb.toString();
+            }
+            case "sqlite" -> {
+                // SQLite: host/port 무의미. database_name 을 파일 경로로 사용 (비면 in-memory)
+                url = "jdbc:sqlite:" + (database != null && !database.isBlank() ? database : ":memory:");
+            }
+            default -> {
+                Map<String, Object> result = new LinkedHashMap<>();
+                result.put("success", false);
+                result.put("message", "지원하지 않는 DB 타입입니다: " + dbType);
+                return result;
+            }
         }
 
         try (Connection c = DriverManager.getConnection(url, props);
@@ -328,7 +360,11 @@ public class ExternalDbConnectionService extends BaseService {
             Map<String, Object> result = new LinkedHashMap<>();
             result.put("success", true);
             result.put("message", "연결 성공");
-            result.put("details", Map.of("host", host, "database", database, "port", port));
+            Map<String, Object> details = new LinkedHashMap<>();
+            details.put("host", host == null ? "" : host);
+            details.put("database", database == null ? "" : database);
+            details.put("port", port);
+            result.put("details", details);
             return result;
         } catch (SQLException e) {
             log.warn("DB 연결 테스트 실패 ({}): {}", url, e.getMessage());
@@ -342,6 +378,16 @@ public class ExternalDbConnectionService extends BaseService {
         }
     }
 
+    private int defaultPort(String dbType) {
+        if (dbType == null) return 5432;
+        return switch (dbType.toLowerCase()) {
+            case "mysql", "mariadb" -> 3306;
+            case "mssql", "sqlserver" -> 1433;
+            case "sqlite" -> 0;
+            default -> 5432;
+        };
+    }
+
     // ── SQL 쿼리 실행 (SELECT only) ────────────────────────────────────────────
 
     public Map<String, Object> executeQuery(long id, String sql) {
diff --git a/backend-spring/src/main/resources/mapper/externalDbConnection.xml b/backend-spring/src/main/resources/mapper/externalDbConnection.xml
index e0da15c8..ad9fda03 100644
--- a/backend-spring/src/main/resources/mapper/externalDbConnection.xml
+++ b/backend-spring/src/main/resources/mapper/externalDbConnection.xml
@@ -166,13 +166,13 @@
         , #{description}
         , #{db_type}
         , #{host}
-        , #{port}
+        , #{port}::varchar
         , #{database_name}
         , #{username}
         , #{password}
-        , #{connection_timeout}
-        , #{query_timeout}
-        , #{max_connections}
+        , #{connection_timeout}::varchar
+        , #{query_timeout}::varchar
+        , #{max_connections}::varchar
         , #{ssl_enabled}
         , #{ssl_cert_path}
         , #{connection_options}::JSONB
@@ -193,13 +193,13 @@
       <if test="description != null">DESCRIPTION = #{description},</if>
       <if test="db_type != null">DB_TYPE = #{db_type},</if>
       <if test="host != null">HOST = #{host},</if>
-      <if test="port != null">PORT = #{port},</if>
+      <if test="port != null">PORT = #{port}::varchar,</if>
       <if test="database_name != null">DATABASE_NAME = #{database_name},</if>
       <if test="username != null">USERNAME = #{username},</if>
       <if test="password != null">PASSWORD = #{password},</if>
-      <if test="connection_timeout != null">CONNECTION_TIMEOUT = #{connection_timeout},</if>
-      <if test="query_timeout != null">QUERY_TIMEOUT = #{query_timeout},</if>
-      <if test="max_connections != null">MAX_CONNECTIONS = #{max_connections},</if>
+      <if test="connection_timeout != null">CONNECTION_TIMEOUT = #{connection_timeout}::varchar,</if>
+      <if test="query_timeout != null">QUERY_TIMEOUT = #{query_timeout}::varchar,</if>
+      <if test="max_connections != null">MAX_CONNECTIONS = #{max_connections}::varchar,</if>
       <if test="ssl_enabled != null">SSL_ENABLED = #{ssl_enabled},</if>
       <if test="ssl_cert_path != null">SSL_CERT_PATH = #{ssl_cert_path},</if>
       <if test="connection_options != null">CONNECTION_OPTIONS = #{connection_options}::JSONB,</if>
diff --git a/frontend/components/admin/ExternalDbConnectionModal.tsx b/frontend/components/admin/ExternalDbConnectionModal.tsx
index 28b2ad46..dbe2f146 100644
--- a/frontend/components/admin/ExternalDbConnectionModal.tsx
+++ b/frontend/components/admin/ExternalDbConnectionModal.tsx
@@ -312,14 +312,14 @@ export const ExternalDbConnectionModal: React.FC<ExternalDbConnectionModalProps>
 
   return (
     <Dialog open={isOpen} onOpenChange={onClose}>
-      <DialogContent className="max-h-[90vh] max-w-[95vw] overflow-hidden sm:max-w-2xl">
-        <DialogHeader>
+      <DialogContent className="flex max-h-[90vh] max-w-[95vw] flex-col overflow-hidden sm:max-w-2xl">
+        <DialogHeader className="shrink-0">
           <DialogTitle className="text-base sm:text-lg">
             {isEditMode ? "연결 정보 수정" : "새 외부 DB 연결 추가"}
           </DialogTitle>
         </DialogHeader>
 
-        <div className="space-y-3 sm:space-y-4">
+        <div className="-mr-1 min-h-0 flex-1 space-y-3 overflow-y-auto pr-1 sm:space-y-4">
           {/* 기본 정보 */}
           <div className="space-y-3 sm:space-y-4">
             <h3 className="text-sm font-semibold sm:text-base">기본 정보</h3>
@@ -607,7 +607,7 @@ export const ExternalDbConnectionModal: React.FC<ExternalDbConnectionModalProps>
           </div>
         </div>
 
-        <DialogFooter className="gap-2 sm:gap-0">
+        <DialogFooter className="shrink-0 gap-2 sm:gap-0">
           <Button
             variant="outline"
             onClick={onClose}