A simple template for PlantUML to draw ER diagram.The basic idea comes from http://plantuml.sourceforge.net/qa/?qa=331/database-modeling

example.puml

@startuml
' uncomment the line below if you're using computer with a retina display
' skinparam dpi 300
!define Table(name,desc) class name as "desc" << (T,#FFAAAA) >>
' we use bold for primary key
' green color for unique
' and underscore for not_null
!define primary_key(x) <b>x</b>
!define unique(x) <color:green>x</color>
!define not_null(x) <u>x</u>
' other tags available:
' <i></i>
' <back:COLOR></color>, where color is a color name or html color code
' (#FFAACC)
' see: http://plantuml.com/classes.html#More
hide methods
hide stereotypes

' entities

Table(user, "user\n(User in our system)") {
primary_key(id) INTEGER
not_null(unique(username)) VARCHAR[32]
not_null(password) VARCHAR[64]
}

Table(session, "session\n(session for user)") {
primary_key(id) INTEGER
not_null(user_id) INTEGER
not_null(unique(session_id)) VARCHAR[64]
}

Table(user_profile, "user_profile\n(Some info of user)") {
primary_key(user_id) INTEGER
age SMALLINT
gender SMALLINT
birthday DATETIME
}

Table(group, "group\n(group of users)") {
primary_key(id) INTEGER
not_null(name) VARCHAR[32]
}

Table(user_group, "user_group\n(relationship of user and group)") {
primary_key(user_id) INTEGER
primary_key(group_id) INTEGER
joined_at DATETIME
}

' relationships
' one-to-one relationship
user -- user_profile : "A user only \nhas one profile"
' one to may relationship
user --> session : "A user may have\n many sessions"
' many to many relationship
' Add mark if you like
user "1" --> "*" user_group : "A user may be \nin many groups"
group "1" --> "0..N" user_group : "A group may \ncontain many users"
@enduml

example.svg

sqlite2plantuml_alt.sh

#/bin/bash -xv
# Alternative plantuml generation
DB=$1
DB_SQLOUT=${DB%.*}.sql
DB_PLANTUML=${DB%.*}.plantuml
sqlite3  ${DB} <<ENDDUMP
.output $DB_SQLOUT
.dump
.exit
ENDDUMP


cat > $DB_PLANTUML <<'PLANTHEADEND'
@startuml
' Template from https://www.red-gate.com/simple-talk/sql/sql-tools/automatically-creating-uml-database-diagrams-for-sql-server/
' uncomment the line below if you're using computer with a retina display
'skinparam dpi 300

!define table(x,desc,group) class group.x as "desc" << (T,mistyrose) >> 
!define view(x) class x << (V,lightblue) >> 
!define tr(x) class x << (R,red) >> 
!define tf(x) class x << (F,darkorange) >> 
!define af(x) class x << (F,white) >> 
!define fn(x) class x << (F,plum) >> 
!define fs(x) class x << (F,tan) >> 
!define ft(x) class x << (F,wheat) >> 
!define if(x) class x << (F,gaisboro) >> 
!define p(x) class x << (P,indianred) >> 
!define pc(x) class x << (P,lemonshiffon) >> 
!define x(x) class x << (P,linen) >>

hide methods 
hide stereotypes 
skinparam classarrowcolor gray

' entities
PLANTHEADEND

# Append table definitions
perl -n -e '
  if(/CREATE TABLE (?:IF NOT EXISTS )?"?(\S+?)"?\((.*)\);/i) {
    print "table($1,$1,db) {\n";
    @fieldSpecs=split(/,(?=[^0-9])/,$2);
    foreach my $field (@fieldSpecs) {
	  $field=~s/\(/<U+0028>/g;
	  $field=~s/\)/<U+0029>/g;
      if($field=~/("?\S+"?) (.*) primary key/) {
         print "  $1: $2 <<pk>>\n";
      } elsif($field=~/(\S+) (.*)/) {
         print "  $1: $2\n";
      } else {
         print "  $field\n";
      }
    }
    print "}\n\n";
  }  
' $DB_SQLOUT >> $DB_PLANTUML


# Append example for manually adding relationships 

cat >> $DB_PLANTUML<<'ENDOFRELATIONS'
' relationships
'
' Examples:
' one-to-one relationship
' Example: user -- user_profile : "A user only \nhas one profile"
' one to may relationship
' Example: user --> session : "A user may have\n many sessions"
' many to many relationship
' Add mark if you like
' Example: user "1" --> "*" user_group : "A user may be \nin many groups"
' Example : group "1" --> "0..N" user_group : "A group may \ncontain many users"
@enduml
ENDOFRELATIONS

sqlite3ToPlantUml.sh

#/bin/bash
# Quick script to generate PlantUml from SQLITE3 database.
# Licence: Public Domain - Created by Ynamics .
DB=$1
DB_SQLOUT=${DB%.*}.sql
DB_PLANTUML=${DB%%.*}.plantuml
sqlite3  ${DB} <<ENDDUMP
.output $DB_SQLOUT
.dump
.exit
ENDDUMP


cat > $DB_PLANTUML <<'PLANTHEADEND'
@startuml
' Template from https://gist.github.com/QuantumGhost/0955a45383a0b6c0bc24f9654b3cb561
' uncomment the line below if you're using computer with a retina display
'skinparam dpi 300
!define Table(name,desc) class name as "desc" << (T,#FFAAAA) >>
' we use bold for primary key
' green color for unique
' and underscore for not_null
!define primary_key(x) <b>x</b>
!define unique(x) <color:green>x</color>
!define not_null(x) <u>x</u>
' other tags available:
' <i></i>
' <back:COLOR></color>, where color is a color name or html color code
' (#FFAACC)
' see: http://plantuml.com/classes.html#More
hide methods
hide stereotypes

' entities
PLANTHEADEND

# Append table definitions
perl -n -e '
  if(/CREATE TABLE (\S+)\((.*)\);/) {
    print "Table($1,\"$1\") {\n";
    @fieldSpecs=split(/,/,$2);
    foreach my $field (@fieldSpecs) {
      if($field=~/(\S+) (.*) primary key/) {
         print "  primary_key($1) $2\n";
      } else {
         print "  $field\n";
      }
    }
    print "}\n\n";
  }  
' $DB_SQLOUT >> $DB_PLANTUML


# Append example for manually adding relationships 

cat >> $DB_PLANTUML<<'ENDOFRELATIONS'
' relationships
'
' Examples:
' one-to-one relationship
' Example: user -- user_profile : "A user only \nhas one profile"
' one to may relationship
' Example: user --> session : "A user may have\n many sessions"
' many to many relationship
' Add mark if you like
' Example: user "1" --> "*" user_group : "A user may be \nin many groups"
' Example : group "1" --> "0..N" user_group : "A group may \ncontain many users"

@enduml
ENDOFRELATIONS

template.puml

@startuml
' uncomment the line below if you're using computer with a retina display
' skinparam dpi 300
!define Table(name,desc) class name as "desc" << (T,#FFAAAA) >>
' we use bold for primary key
' green color for unique
' and underscore for not_null
!define primary_key(x) <b>x</b>
!define unique(x) <color:green>x</color>
!define not_null(x) <u>x</u>
' other tags available:
' <i></i>
' <back:COLOR></color>, where color is a color name or html color code
' (#FFAACC)
' see: http://plantuml.com/classes.html#More
hide methods
hide stereotypes

' entities

' relationships

@enduml