diff --git a/.circleci/config.yml b/.circleci/config.yml
index 659d7ea..4a94dae 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -21,6 +21,7 @@ jobs:
       - run: CON_STRING=$TEST_DATABASE_URL cargo test
       - run: cargo build --release
       - run: ./target/release/sqlant $TEST_DATABASE_URL
+      - run: ./target/release/sqlant $TEST_DATABASE_URL --nn
     resource_class: small
 
 
diff --git a/Cargo.lock b/Cargo.lock
index c3ab840..3f31cfe 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4,9 +4,9 @@ version = 3
 
 [[package]]
 name = "async-trait"
-version = "0.1.56"
+version = "0.1.57"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "96cf8829f67d2eab0b2dfa42c5d0ef737e0724e4a82b01b3e292456202b19716"
+checksum = "76464446b8bc32758d7e88ee1a804d9914cd9b1cb264c029899680b0be29826f"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -33,9 +33,9 @@ checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
 [[package]]
 name = "block-buffer"
-version = "0.10.2"
+version = "0.10.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0bf7fe51849ea569fd452f37822f606a5cabb684dc918707a0193fd4664ff324"
+checksum = "69cce20737498f97b993470a6e536b8523f0af7892a4f928cceb1ac5e52ebe7e"
 dependencies = [
  "generic-array",
 ]
@@ -48,9 +48,9 @@ checksum = "14c189c53d098945499cdfa7ecc63567cf3886b3332b312a5b4585d8d3a6a610"
 
 [[package]]
 name = "bytes"
-version = "1.1.0"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c4872d67bab6358e59559027aa3b9157c53d9358c51423c17554809a8858e0f8"
+checksum = "ec8a7b6a70fde80372154c65702f00a0f56f3e1c36abbc6c440484be248856db"
 
 [[package]]
 name = "cfg-if"
@@ -60,18 +60,18 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "cpufeatures"
-version = "0.2.2"
+version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "59a6001667ab124aebae2a495118e11d30984c3a653e99d86d58971708cf5e4b"
+checksum = "28d997bd5e24a5928dd43e46dc529867e207907fe0b239c3477d924f7f2ca320"
 dependencies = [
  "libc",
 ]
 
 [[package]]
 name = "crypto-common"
-version = "0.1.5"
+version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2ccfd8c0ee4cce11e45b3fd6f9d5e69e0cc62912aa6a0cb1bf4617b0eba5a12f"
+checksum = "1bfb12502f3fc46cca1bb51ac28df9d618d813cdc3d2f25b9fe775a34af26bb3"
 dependencies = [
  "generic-array",
  "typenum",
@@ -79,9 +79,9 @@ dependencies = [
 
 [[package]]
 name = "digest"
-version = "0.10.3"
+version = "0.10.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f2fb860ca6fafa5552fb6d0e816a69c8e49f0908bf524e30a90d97c85892d506"
+checksum = "adfbc57365a37acbd2ebf2b64d7e69bb766e2fea813521ed536f5d0520dcf86c"
 dependencies = [
  "block-buffer",
  "crypto-common",
@@ -94,26 +94,11 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4443176a9f2c162692bd3d352d745ef9413eec5782a80d8fd6f8a1ac692a07f7"
 
-[[package]]
-name = "futures"
-version = "0.3.21"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f73fe65f54d1e12b726f517d3e2135ca3125a437b6d998caf1962961f7172d9e"
-dependencies = [
- "futures-channel",
- "futures-core",
- "futures-executor",
- "futures-io",
- "futures-sink",
- "futures-task",
- "futures-util",
-]
-
 [[package]]
 name = "futures-channel"
-version = "0.3.21"
+version = "0.3.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c3083ce4b914124575708913bca19bfe887522d6e2e6d0952943f5eac4a74010"
+checksum = "30bdd20c28fadd505d0fd6712cdfcb0d4b5648baf45faef7f852afb2399bb050"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -121,32 +106,15 @@ dependencies = [
 
 [[package]]
 name = "futures-core"
-version = "0.3.21"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0c09fd04b7e4073ac7156a9539b57a484a8ea920f79c7c675d05d289ab6110d3"
-
-[[package]]
-name = "futures-executor"
-version = "0.3.21"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9420b90cfa29e327d0429f19be13e7ddb68fa1cccb09d65e5706b8c7a749b8a6"
-dependencies = [
- "futures-core",
- "futures-task",
- "futures-util",
-]
-
-[[package]]
-name = "futures-io"
-version = "0.3.21"
+version = "0.3.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fc4045962a5a5e935ee2fdedaa4e08284547402885ab326734432bed5d12966b"
+checksum = "4e5aa3de05362c3fb88de6531e6296e85cde7739cccad4b9dfeeb7f6ebce56bf"
 
 [[package]]
 name = "futures-macro"
-version = "0.3.21"
+version = "0.3.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "33c1e13800337f4d4d7a316bf45a567dbcb6ffe087f16424852d97e97a91f512"
+checksum = "42cd15d1c7456c04dbdf7e88bcd69760d74f3a798d6444e16974b505b0e62f17"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -155,29 +123,26 @@ dependencies = [
 
 [[package]]
 name = "futures-sink"
-version = "0.3.21"
+version = "0.3.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "21163e139fa306126e6eedaf49ecdb4588f939600f0b1e770f4205ee4b7fa868"
+checksum = "21b20ba5a92e727ba30e72834706623d94ac93a725410b6a6b6fbc1b07f7ba56"
 
 [[package]]
 name = "futures-task"
-version = "0.3.21"
+version = "0.3.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "57c66a976bf5909d801bbef33416c41372779507e7a6b3a5e25e4749c58f776a"
+checksum = "a6508c467c73851293f390476d4491cf4d227dbabcd4170f3bb6044959b294f1"
 
 [[package]]
 name = "futures-util"
-version = "0.3.21"
+version = "0.3.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d8b7abd5d659d9b90c8cba917f6ec750a74e2dc23902ef9cd4cc8c8b22e6036a"
+checksum = "44fb6cb1be61cc1d2e43b262516aafcf63b241cffdb1d3fa115f91d9c7b09c90"
 dependencies = [
- "futures-channel",
  "futures-core",
- "futures-io",
  "futures-macro",
  "futures-sink",
  "futures-task",
- "memchr",
  "pin-project-lite",
  "pin-utils",
  "slab",
@@ -185,9 +150,9 @@ dependencies = [
 
 [[package]]
 name = "generic-array"
-version = "0.14.5"
+version = "0.14.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fd48d33ec7f05fbfa152300fdad764757cbded343c1aa1cff2fbaf4134851803"
+checksum = "bff49e947297f3312447abdca79f45f4738097cc82b06e72054d2223f601f1b9"
 dependencies = [
  "typenum",
  "version_check",
@@ -221,15 +186,15 @@ checksum = "6c8af84674fe1f223a982c933a0ee1086ac4d4052aa0fb8060c12c6ad838e754"
 
 [[package]]
 name = "libc"
-version = "0.2.126"
+version = "0.2.133"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "349d5a591cd28b49e1d1037471617a32ddcda5731b99419008085f72d5a53836"
+checksum = "c0f80d65747a3e43d1596c7c5492d95d5edddaabd45a7fcdb02b95f644164966"
 
 [[package]]
 name = "lock_api"
-version = "0.4.7"
+version = "0.4.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "327fa5b6a6940e4699ec49a9beae1ea4845c6bab9314e4f84ac68742139d8c53"
+checksum = "435011366fe56583b16cf956f9df0095b405b82d76425bc8981c0e22e60ec4df"
 dependencies = [
  "autocfg",
  "scopeguard",
@@ -246,9 +211,9 @@ dependencies = [
 
 [[package]]
 name = "md-5"
-version = "0.10.1"
+version = "0.10.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "658646b21e0b72f7866c7038ab086d3d5e1cd6271f060fd37defb241949d0582"
+checksum = "6365506850d44bff6e2fbcb5176cf63650e48bd45ef2fe2665ae1570e0f4b9ca"
 dependencies = [
  "digest",
 ]
@@ -273,9 +238,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.13.0"
+version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "18a6dbe30758c9f83eb00cbea4ac95966305f5a7772f3f42ebfc7fc7eddbd8e1"
+checksum = "e82dad04139b71a90c080c8463fe0dc7902db5192d939bd0950f074d014339e1"
 
 [[package]]
 name = "parking_lot"
@@ -302,24 +267,24 @@ dependencies = [
 
 [[package]]
 name = "percent-encoding"
-version = "2.1.0"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d4fd5641d01c8f18a23da7b6fe29298ff4b55afcccdf78973b24cf3175fee32e"
+checksum = "478c572c3d73181ff3c2539045f6eb99e5491218eae919370993b890cdbdd98e"
 
 [[package]]
 name = "phf"
-version = "0.10.1"
+version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fabbf1ead8a5bcbc20f5f8b939ee3f5b0f6f281b6ad3468b84656b658b455259"
+checksum = "928c6535de93548188ef63bb7c4036bd415cd8f36ad25af44b9789b2ee72a48c"
 dependencies = [
  "phf_shared",
 ]
 
 [[package]]
 name = "phf_shared"
-version = "0.10.0"
+version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b6796ad771acdc0123d2a88dc428b5e38ef24456743ddb1744ed628f9815c096"
+checksum = "e1fb5f6f826b772a8d4c0394209441e7d37cbbb967ae9c7e0e8134365c9ee676"
 dependencies = [
  "siphasher",
 ]
@@ -338,13 +303,13 @@ checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
 [[package]]
 name = "postgres"
-version = "0.19.3"
+version = "0.19.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c8bbcd5f6deb39585a0d9f4ef34c4a41c25b7ad26d23c75d837d78c8e7adc85f"
+checksum = "960c214283ef8f0027974c03e9014517ced5db12f021a9abb66185a5751fab0a"
 dependencies = [
  "bytes",
  "fallible-iterator",
- "futures",
+ "futures-util",
  "log",
  "tokio",
  "tokio-postgres",
@@ -370,9 +335,9 @@ dependencies = [
 
 [[package]]
 name = "postgres-types"
-version = "0.2.3"
+version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ebd6e8b7189a73169290e89bd24c771071f1012d8fe6f738f5226531f0b03d89"
+checksum = "73d946ec7d256b04dfadc4e6a3292324e6f417124750fc5c0950f981b703a0f1"
 dependencies = [
  "bytes",
  "fallible-iterator",
@@ -387,18 +352,18 @@ checksum = "eb9f9e6e233e5c4a35559a617bf40a4ec447db2e84c20b55a6f83167b7e57872"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.40"
+version = "1.0.44"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dd96a1e8ed2596c337f8eae5f24924ec83f5ad5ab21ea8e455d3566c69fbcaf7"
+checksum = "7bd7356a8122b6c4a24a82b278680c73357984ca2fc79a0f9fa6dea7dced7c58"
 dependencies = [
  "unicode-ident",
 ]
 
 [[package]]
 name = "quote"
-version = "1.0.20"
+version = "1.0.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3bcdf212e9776fbcb2d23ab029360416bb1706b1aea2d1a5ba002727cbcab804"
+checksum = "bbe448f377a7d6961e30f5955f9b8d106c3f5e449d493ee1b125c1d43c2b5179"
 dependencies = [
  "proc-macro2",
 ]
@@ -426,18 +391,18 @@ dependencies = [
 
 [[package]]
 name = "rand_core"
-version = "0.6.3"
+version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d34f1408f55294453790c48b2f1ebbb1c5b4b7563eb1f418bcfcfdbb06ebb4e7"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
 dependencies = [
  "getrandom",
 ]
 
 [[package]]
 name = "redox_syscall"
-version = "0.2.13"
+version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "62f25bc4c7e55e0b0b7a1d43fb893f4fa1361d0abe38b9ce4f323c2adfe6ef42"
+checksum = "fb5a58c1855b4b6819d59012155603f0b22ad30cad752600aadfcb695265519a"
 dependencies = [
  "bitflags",
 ]
@@ -456,18 +421,18 @@ checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
 [[package]]
 name = "serde"
-version = "1.0.144"
+version = "1.0.145"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0f747710de3dcd43b88c9168773254e809d8ddbdf9653b84e2554ab219f17860"
+checksum = "728eb6351430bccb993660dfffc5a72f91ccc1295abaa8ce19b27ebe4f75568b"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.144"
+version = "1.0.145"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "94ed3a816fb1d101812f83e789f888322c34e291f894f19590dc310963e87a00"
+checksum = "81fa1584d3d1bcacd84c277a0dfe21f5b0f6accf4a23d04d4c6d61f1af522b4c"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -487,9 +452,9 @@ dependencies = [
 
 [[package]]
 name = "sha2"
-version = "0.10.2"
+version = "0.10.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "55deaec60f81eefe3cce0dc50bda92d6d8e88f2a27df7c5033b42afeb1ed2676"
+checksum = "82e6b795fe2e3b1e845bafcb27aa35405c4d47cdfc92af5fc8d3002f76cebdc0"
 dependencies = [
  "cfg-if",
  "cpufeatures",
@@ -504,9 +469,12 @@ checksum = "7bd3e3206899af3f8b12af284fafc038cc1dc2b41d1b89dd17297221c5d225de"
 
 [[package]]
 name = "slab"
-version = "0.4.6"
+version = "0.4.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eb703cfe953bccee95685111adeedb76fabe4e97549a58d16f03ea7b9367bb32"
+checksum = "4614a76b2a8be0058caa9dbbaf66d988527d86d003c11a94fbd335d7661edcef"
+dependencies = [
+ "autocfg",
+]
 
 [[package]]
 name = "smallvec"
@@ -516,9 +484,9 @@ checksum = "2fd0db749597d91ff862fd1d55ea87f7855a744a8425a64695b6fca237d1dad1"
 
 [[package]]
 name = "socket2"
-version = "0.4.4"
+version = "0.4.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "66d72b759436ae32898a2af0a14218dbf55efde3feeb170eb623637db85ee1e0"
+checksum = "02e2d2db9033d13a1567121ddd7a095ee144db4e1ca1b1bda3419bc0da294ebd"
 dependencies = [
  "libc",
  "winapi",
@@ -526,7 +494,7 @@ dependencies = [
 
 [[package]]
 name = "sqlant"
-version = "0.1.1"
+version = "0.1.2"
 dependencies = [
  "postgres",
  "serde",
@@ -551,9 +519,9 @@ checksum = "6bdef32e8150c2a081110b42772ffe7d7c9032b606bc226c8260fd97e0976601"
 
 [[package]]
 name = "syn"
-version = "1.0.98"
+version = "1.0.100"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c50aef8a904de4c23c788f104b7dddc7d6f79c647c7c8ce4cc8f73eb0ca773dd"
+checksum = "52205623b1b0f064a4e71182c3b18ae902267282930c6d5462c91b859668426e"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -587,9 +555,9 @@ checksum = "cda74da7e1a664f795bb1f8a87ec406fb89a02522cf6e50620d016add6dbbf5c"
 
 [[package]]
 name = "tokio"
-version = "1.20.0"
+version = "1.21.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "57aec3cfa4c296db7255446efb4928a6be304b431a806216105542a67b6ca82e"
+checksum = "0020c875007ad96677dcc890298f4b942882c5d4eb7cc8f439fc3bf813dc9c95"
 dependencies = [
  "autocfg",
  "bytes",
@@ -604,15 +572,16 @@ dependencies = [
 
 [[package]]
 name = "tokio-postgres"
-version = "0.7.6"
+version = "0.7.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "19c88a47a23c5d2dc9ecd28fb38fba5fc7e5ddc1fe64488ec145076b0c71c8ae"
+checksum = "29a12c1b3e0704ae7dfc25562629798b29c72e6b1d0a681b6f29ab4ae5e7f7bf"
 dependencies = [
  "async-trait",
  "byteorder",
  "bytes",
  "fallible-iterator",
- "futures",
+ "futures-channel",
+ "futures-util",
  "log",
  "parking_lot",
  "percent-encoding",
@@ -627,9 +596,9 @@ dependencies = [
 
 [[package]]
 name = "tokio-util"
-version = "0.7.3"
+version = "0.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cc463cd8deddc3770d20f9852143d50bf6094e640b485cb2e189a2099085ff45"
+checksum = "0bb2e075f03b3d66d8d8785356224ba688d2906a371015e225beeb65ca92c740"
 dependencies = [
  "bytes",
  "futures-core",
@@ -641,9 +610,9 @@ dependencies = [
 
 [[package]]
 name = "tracing"
-version = "0.1.35"
+version = "0.1.36"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a400e31aa60b9d44a52a8ee0343b5b18566b03a8321e0d321f695cf56e940160"
+checksum = "2fce9567bd60a67d08a16488756721ba392f24f29006402881e43b19aac64307"
 dependencies = [
  "cfg-if",
  "pin-project-lite",
@@ -652,9 +621,9 @@ dependencies = [
 
 [[package]]
 name = "tracing-core"
-version = "0.1.28"
+version = "0.1.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7b7358be39f2f274f322d2aaed611acc57f382e8eb1e5b48cb9ae30933495ce7"
+checksum = "5aeea4303076558a00714b823f9ad67d58a3bbda1df83d8827d21193156e22f7"
 dependencies = [
  "once_cell",
 ]
@@ -673,15 +642,15 @@ checksum = "099b7128301d285f79ddd55b9a83d5e6b9e97c92e0ea0daebee7263e932de992"
 
 [[package]]
 name = "unicode-ident"
-version = "1.0.2"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "15c61ba63f9235225a22310255a29b806b907c9b8c964bcbd0a2c70f3f2deea7"
+checksum = "dcc811dc4066ac62f84f11307873c4850cb653bfa9b1719cee2bd2204a4bc5dd"
 
 [[package]]
 name = "unicode-normalization"
-version = "0.1.21"
+version = "0.1.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "854cbdc4f7bc6ae19c820d44abdc3277ac3e1b2b93db20a636825d9322fb60e6"
+checksum = "5c5713f0fc4b5db668a2ac63cdb7bb4469d8c9fed047b1d0292cc7b0ce2ba921"
 dependencies = [
  "tinyvec",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index d91464d..cb1b4a7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "sqlant"
-version = "0.1.1"
+version = "0.1.2"
 edition = "2021"
 license = "MIT"
 repository = "https://github.com/kurotych/sqlant"
diff --git a/src/lib.rs b/src/lib.rs
index 8823cb7..687dc69 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,7 +4,15 @@ pub mod sql_entities;
 
 use plantuml_generator::PlantUmlDefaultGenerator;
 use psql_erd_loader::PostgreSqlERDLoader;
-use sql_entities::{PlantUmlGenerator, SqlERDataLoader};
+use sql_entities::{SqlERData, SqlERDataLoader};
+
+pub struct GeneratorConfigOptions {
+    pub not_null: bool,
+}
+
+pub trait PlantUmlGenerator {
+    fn generate(&self, sql_erd: &SqlERData, opts: &GeneratorConfigOptions) -> String;
+}
 
 pub fn lookup_parser(connection_string: &str) -> Box<dyn SqlERDataLoader> {
     if connection_string.starts_with("postgresql") {
diff --git a/src/main.rs b/src/main.rs
index 8e420a1..5744ab5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,14 +1,40 @@
-use sqlant::{get_generator, lookup_parser};
-use std::env;
+use sqlant::{get_generator, lookup_parser, GeneratorConfigOptions};
+use std::{env, process::exit};
+
+fn print_program_info() {
+    println!(
+        "Generate PlantUML ER diagram textual description from SQL connection string\n\
+        USAGE: sqlant <conn> [OPTIONS]\n\
+        \tExample: sqlant postgresql://sqlant_user:sqlant_pswd@localhost/sqlant_db --nn\n\
+        OPTIONS:"
+    );
+    println!("\t-n, --nn {:>42}\n", "Add NOT_NULL(NN) marks");
+}
+
+fn parse_arguments(args: &mut Vec<String>) -> GeneratorConfigOptions {
+    while !args.is_empty() {
+        let arg = args.pop().unwrap();
+        if arg == "-n" || arg == "--nn" {
+            return GeneratorConfigOptions { not_null: true };
+        }
+        eprintln!("Unknown argument {:?}", arg);
+        exit(2);
+    }
+    GeneratorConfigOptions { not_null: false }
+}
 
 fn main() {
-    let args: Vec<String> = env::args().collect();
+    let mut args: Vec<String> = env::args().collect();
     // Look at clap if you'll need more complicated CLI experience
     // https://docs.rs/clap/latest/clap/
-    assert!(args.len() == 2, "Usage: sqlant <conn>");
+    if args.len() < 2 {
+        print_program_info();
+        exit(1);
+    }
+
     let mut s = lookup_parser(&args[1]);
     let erd = s.load_erd_data();
     let rndr = get_generator();
-    let result = rndr.generate(&erd);
+    let result = rndr.generate(&erd, &parse_arguments(&mut args.split_off(2)));
     println!("{result}")
 }
diff --git a/src/plantuml_generator.rs b/src/plantuml_generator.rs
index 150a910..fd1a0a3 100644
--- a/src/plantuml_generator.rs
+++ b/src/plantuml_generator.rs
@@ -1,4 +1,5 @@
-use super::sql_entities::{PlantUmlGenerator, SqlERData, Table, TableColumn};
+use super::sql_entities::{SqlERData, Table, TableColumn};
+use crate::{GeneratorConfigOptions, PlantUmlGenerator};
 use serde::Serialize;
 use tinytemplate::{format_unescaped, TinyTemplate};
 
@@ -14,7 +15,8 @@ static ENTITY_TEMPLATE: &'static str = "entity \"**{name}**\" \\{\n{pks}---\n{fk
 
 static COLUMN_TEMPLATE: &'static str =
     "{{ if is_pk }}#{{else}}*{{ endif }} <b>\"\"{col.name}\"\"</b>: //\"\"{col.datatype}\"\" \
-        <b>{{ if is_pk }}<color:goldenrod>(PK) </color>{{ endif }}{{ if is_fk }}<color:701fc6>(FK) </color>{{ endif }} //\n";
+        {{ if is_pk }}<b><color:goldenrod>(PK) </color></b>{{ endif }}{{ if is_fk }}<b><color:701fc6>(FK) </color></b>{{ endif }}\
+        {{ if is_nn }}<b><color:DarkRed>(NN) </color></b>{{ endif }} //\n";
 
 static REL_TEMPLATE: &'static str =
     "\"**{source_table_name}**\" {{ if is_zero_one_to_one }}|o--||{{else}}}o--||{{ endif }} \"**{target_table_name}**\"\n";
@@ -29,6 +31,7 @@ struct SColumn<'a> {
     col: &'a TableColumn,
     is_fk: bool,
     is_pk: bool,
+    is_nn: bool,
 }
 
 #[derive(Serialize)]
@@ -63,7 +66,7 @@ impl<'a> PlantUmlDefaultGenerator<'a> {
         PlantUmlDefaultGenerator { str_templates }
     }
 
-    fn entity_render(&self, tbl: &Table) -> String {
+    fn entity_render(&self, tbl: &Table, opts: &GeneratorConfigOptions) -> String {
         // if pk_render - render only pk columns
         // if fk_render - render only pure FK columns (Non PK)
         // if both are false return non pk and non fk
@@ -91,6 +94,7 @@ impl<'a> PlantUmlDefaultGenerator<'a> {
                                 col: col.as_ref(),
                                 is_fk: col.is_fk(),
                                 is_pk: col.is_pk(),
+                                is_nn: opts.not_null && col.is_nn(),
                             },
                         )
                         .unwrap()
@@ -111,11 +115,11 @@ impl<'a> PlantUmlDefaultGenerator<'a> {
 }
 
 impl<'a> PlantUmlGenerator for PlantUmlDefaultGenerator<'a> {
-    fn generate(&self, sql_erd: &SqlERData) -> String {
+    fn generate(&self, sql_erd: &SqlERData, opts: &GeneratorConfigOptions) -> String {
         let entities: Vec<String> = sql_erd
             .tables
             .iter()
-            .map(|tbl| self.entity_render(&tbl))
+            .map(|tbl| self.entity_render(&tbl, opts))
             .collect();
         let foreign_keys: Vec<String> = sql_erd
             .foreign_keys
diff --git a/src/sql_entities.rs b/src/sql_entities.rs
index cfdc987..42bdfb6 100644
--- a/src/sql_entities.rs
+++ b/src/sql_entities.rs
@@ -20,6 +20,9 @@ impl TableColumn {
     pub fn is_fk(&self) -> bool {
         self.constraints.contains(&ColumnConstraints::ForeignKey)
     }
+    pub fn is_nn(&self) -> bool {
+        self.constraints.contains(&ColumnConstraints::NotNull)
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize)]
@@ -61,10 +64,6 @@ pub trait SqlERDataLoader {
     fn load_erd_data(&mut self) -> SqlERData;
 }
 
-pub trait PlantUmlGenerator {
-    fn generate(&self, sql_erd: &SqlERData) -> String;
-}
-
 impl Table {
     pub fn new(name: String, columns: Vec<Rc<TableColumn>>) -> Table {
         let has_composite_pk = columns.iter().fold(0, |acc, x| {
diff --git a/tests/test_db.sql b/tests/test_db.sql
index aec9299..17962af 100644
--- a/tests/test_db.sql
+++ b/tests/test_db.sql
@@ -34,7 +34,7 @@ create table vendor_address (
   , state text not null
   , city text not null
   , line1 text not null
-  , line2 text not null
+  , line2 text 
   , FOREIGN KEY(vendor_id) REFERENCES vendor (id)
 );