diff --git a/.gitignore b/.gitignore
index cda1742..96d7445 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 node_modules
 ignored_files
+package-lock.json
diff --git a/README.md b/README.md
index 4ac31d7..32a2de1 100644
--- a/README.md
+++ b/README.md
@@ -99,3 +99,38 @@ Options:
   --tu                                Target username, overrides --user
   --tp                                Target password, overrides --password
 ```
+
+### Synchronize two RethinkDB databases without deleting target records that already exist.
+
+`thinker syncinc` Synchronizes tables, indexes and data from the source database to the target database. The target database is modified to match the source but no records from target are deleted.
+
+```bash
+Thinker Sync
+==============================
+
+Sync two RethinkDB databases (without deleting target records).
+
+Usage:
+  thinker syncinc [options]
+  thinker syncinc --sh host[:port] --th host[:port] --sd dbName --td dbName
+  thinker syncinc -h | --help
+
+Options:
+  --sh, --sourceHost=<host[:port]>    Source host, defaults to 'localhost:21015'
+  --th, --targetHost=<host[:port]>    Target host, defaults to 'localhost:21015'
+  --sd, --sourceDB=<dbName>           Source database
+  --td, --targetDB=<dbName>           Target database
+
+  --pt, --pickTables=<table1,table2>  Comma separated list of tables to sync (whitelist)
+  --ot, --omitTables=<table1,table2>  Comma separated list of tables to ignore (blacklist)
+                                      Note: '--pt' and '--ot' are mutually exclusive options.
+
+  --user                              Source and Target username
+  --password                          Source and Target password
+
+  --su                                Source username, overrides --user
+  --sp                                Source password, overrides --password
+
+  --tu                                Target username, overrides --user
+  --tp                                Target password, overrides --password
+```
diff --git a/lib/commands/syncinc.js b/lib/commands/syncinc.js
new file mode 100644
index 0000000..fb261dc
--- /dev/null
+++ b/lib/commands/syncinc.js
@@ -0,0 +1,278 @@
+
+let _ = require('lodash')
+let Promise = require('bluebird')
+let fs = require('fs')
+Promise.promisifyAll(fs)
+let inquirer = require('inquirer')
+let co = require('co')
+let colors = require('colors')
+let asyncEach = require('../asyncEach')
+let blockingQueue = require('../blockingQueue')
+let compareValues = require('../compareValues')
+let moment = require('moment')
+
+let HELPTEXT = `
+
+  Thinker Sync
+  ==============================
+
+  Sync two RethinkDB databases.
+
+  Usage:
+    thinker syncinc [options]
+    thinker syncinc --sh host[:port] --th host[:port] --sd dbName --td dbName
+    thinker syncinc -h | --help
+
+  Options:
+    --sh, --sourceHost=<host[:port]>    Source host, defaults to 'localhost:21015'
+    --th, --targetHost=<host[:port]>    Target host, defaults to 'localhost:21015'
+    --sd, --sourceDB=<dbName>           Source database
+    --td, --targetDB=<dbName>           Target database
+
+    --pt, --pickTables=<table1,table2>  Comma separated list of tables to sync (whitelist)
+    --ot, --omitTables=<table1,table2>  Comma separated list of tables to ignore (blacklist)
+                                        Note: '--pt' and '--ot' are mutually exclusive options.
+
+    --user                              Source and Target username
+    --password                          Source and Target password
+
+    --su                                Source username, overrides --user
+    --sp                                Source password, overrides --password
+
+    --tu                                Target username, overrides --user
+    --tp                                Target password, overrides --password
+
+`
+
+module.exports = function *(argv) {
+  let startTime
+  let sHost = argv.sh ? argv.sh : argv.sourceHost ? argv.sourceHost : 'localhost:28015'
+  let tHost = argv.th ? argv.th : argv.targetHost ? argv.targetHost : 'localhost:28015'
+  let sourceHost = _.first(sHost.split(':'))
+  let targetHost = _.first(tHost.split(':'))
+  let sourcePort = parseInt(_.last(sHost.split(':')), 10) || 28015
+  let targetPort = parseInt(_.last(tHost.split(':')), 10) || 28015
+  let sourceDB = argv.sd ? argv.sd : argv.sourceDB ? argv.sourceDB : null
+  let targetDB = argv.td ? argv.td : argv.targetDB ? argv.targetDB : null
+  let pickTables = argv.pt ? argv.pt : argv.pickTables ? argv.pickTables : null
+  let omitTables = argv.ot ? argv.ot : argv.omitTables ? argv.omitTables : null
+  let sourceUser = argv.su ? argv.su : argv.user ? argv.user : 'admin'
+  let sourcePassword = argv.sp ? argv.sp : argv.password ? argv.password : ''
+  let targetUser = argv.tu ? argv.tu : argv.user ? argv.user : 'admin'
+  let targetPassword = argv.tp ? argv.tp : argv.password ? argv.password : ''
+
+  pickTables = _.isString(pickTables) ? pickTables.split(',') : null
+  omitTables = _.isString(omitTables) ? omitTables.split(',') : null
+
+  if (argv.h || argv.help) {
+    console.log(HELPTEXT)
+    return
+  }
+
+  if (pickTables && omitTables) {
+    console.log('pickTables and omitTables are mutually exclusive options.')
+    return
+  }
+
+  if (!sourceDB || !targetDB) {
+    console.log('Source and target databases are required!')
+    console.log(HELPTEXT)
+    return
+  }
+
+  if (`${sourceHost}:${sourcePort}` === `${targetHost}:${targetPort}` && sourceDB === targetDB) {
+    console.log('Source and target databases must be different if syncing on same server!')
+    return
+  }
+
+  // Verify source database
+  let sr = require('rethinkdbdash')({host: sourceHost, port: sourcePort, user: sourceUser, password: sourcePassword})
+  // get sourceDBList
+  let sourceDBList = yield sr.dbList().run()
+  // get sourceTableList
+  let sourceTableList = yield sr.db(sourceDB).tableList().run()
+  if (!sourceDBList.includes(sourceDB)) {
+    console.log('Source DB does not exist!')
+    return
+  }
+
+  if (pickTables && !_.every(pickTables, (table) => sourceTableList.includes(table))) {
+    console.log(colors.red('Not all the tables specified in --pickTables exist!'))
+    return
+  }
+
+  if (omitTables && !_.every(omitTables, (table) => sourceTableList.includes(table))) {
+    console.log(colors.red('Not all the tables specified in --omitTables exist!'))
+    return
+  }
+
+  let confMessage = `
+    ${colors.green('Ready to synchronize!')}
+    The database '${colors.yellow(sourceDB)}' on '${colors.yellow(sourceHost)}:${colors.yellow(sourcePort)}' will be synchronized to the '${colors.yellow(targetDB)}' database on '${colors.yellow(targetHost)}:${colors.yellow(targetPort)}'
+    This will modify records in the '${colors.yellow(targetDB)}' database on '${colors.yellow(targetHost)}:${colors.yellow(targetPort)}' if it exists!
+  `
+
+  if (pickTables) {
+    confMessage += `  ONLY the following tables will be synchronized: ${colors.yellow(pickTables.join(','))}\n`
+  }
+  if (omitTables) {
+    confMessage += `  The following tables will NOT be synchronized: ${colors.yellow(omitTables.join(','))}\n`
+  }
+
+  console.log(confMessage)
+
+  let answer = yield inquirer.prompt([{
+    type: 'confirm',
+    name: 'confirmed',
+    message: 'Proceed?',
+    default: false
+  }])
+
+  if (!answer.confirmed) {
+    console.log(colors.red('ABORT!'))
+    return
+  }
+
+  startTime = moment()
+
+  let tablesToSync
+  if (pickTables) {
+    tablesToSync = pickTables
+  } else if (omitTables) {
+    tablesToSync = _.difference(sourceTableList, omitTables)
+  } else {
+    tablesToSync = sourceTableList
+  }
+
+  let tr = require('rethinkdbdash')({host: targetHost, port: targetPort, user: targetUser, password: targetPassword})
+
+  let targetDBList = yield tr.dbList().run()
+  if (!targetDBList.includes(targetDB)) {
+    console.log('Target DB does not exist, creating...')
+    yield tr.dbCreate(targetDB).run()
+  }
+
+  let targetDBTableList = yield tr.db(targetDB).tableList().run()
+
+  yield asyncEach(tablesToSync, function *(table, idx) {
+    if (!targetDBTableList.includes(table)) {
+      console.log(`Table '${table}' does not exist on target, creating...`)
+      let primaryKey = yield sr.db(sourceDB).table(table).info()('primary_key').run()
+      yield tr.db(targetDB).tableCreate(table, {primaryKey: primaryKey}).run()
+    }
+  }, 999)
+
+  yield asyncEach(tablesToSync, function *(table, idx) {
+    let sourceIndexes = yield sr.db(sourceDB).table(table).indexList().run()
+    let targetIndexes = yield tr.db(targetDB).table(table).indexList().run()
+
+    for (let index of sourceIndexes) {
+      if (!targetIndexes.includes(index)) {
+        console.log(`Index '${index}' does not exist on '${table}' table on target, creating...`)
+        let indexObj = yield sr.db(sourceDB).table(table).indexStatus(index).run()
+        indexObj = _.first(indexObj)
+        yield tr.db(targetDB).table(table).indexCreate(
+          indexObj.index, indexObj.function, {geo: indexObj.geo, multi: indexObj.multi}
+        ).run()
+      }
+    }
+
+    yield tr.db(targetDB).table(table).indexWait().run()
+  }, 999)
+
+  for (let table of tablesToSync) {
+    let totalRecords = yield sr.db(sourceDB).table(table).count().run()
+    let recordsProcessed = 0
+    let lastRecordsProcessed = 0
+    let perfStat = []
+    let statusInterval = 500
+    let created = 0
+    let updated = 0
+    let deleted = 0
+    let queue = blockingQueue()
+
+    console.log(`Synchronizing ${totalRecords} records in ${table}...                                                                        `)
+    let sourceCursor = yield sr.db(sourceDB).table(table).orderBy({index: sr.asc('id')})
+      .map(function (row) { return {id: row('id'), hash: sr.uuid(row.toJSON())} })
+      .run({cursor: true})
+    let targetCursor = yield tr.db(targetDB).table(table).orderBy({index: tr.asc('id')})
+      .map(function (row) { return {id: row('id'), hash: tr.uuid(row.toJSON())} })
+      .run({cursor: true})
+
+    let si = {}
+    let ti = {}
+
+    si = yield getNextIdx(sourceCursor, si)
+    ti = yield getNextIdx(targetCursor, ti)
+
+    co(function *() {
+      let pc = 0
+      while (pc < 100) {
+        perfStat.unshift(recordsProcessed - lastRecordsProcessed)
+        while (perfStat.length > 30) {
+          perfStat.pop()
+        }
+        let rps = (_.reduce(perfStat, (a, b) => a + b) / (perfStat.length * (statusInterval / 1000))).toFixed(1)
+        pc = ((recordsProcessed / totalRecords) * 100).toFixed(1)
+        process.stdout.write(` RECORDS SYNCHRONIZED: ${recordsProcessed} | ${rps} sec. | %${pc} | created ${created} | updated ${updated} | deleted ${deleted} | concurrency ${queue.concurrency}                    \r`)
+        lastRecordsProcessed = recordsProcessed
+
+        yield Promise.delay(statusInterval)
+      }
+    })
+
+    while (si.id !== Infinity || ti.id !== Infinity) {
+      const cmp = compareValues(si.id, ti.id)
+
+      if (cmp === 0) {  // si.id === ti.id  ->  check hashes
+        let sid = si.id
+        let tid = ti.id
+        if (si.hash !== ti.hash) {
+          yield queue.push(function *() {
+            let record = yield sr.db(sourceDB).table(table).get(sid).run({timeFormat: 'raw'})
+            yield tr.db(targetDB).table(table).get(tid).replace(record).run()
+            updated += 1
+          })
+        }
+        si = yield getNextIdx(sourceCursor, si)
+        ti = yield getNextIdx(targetCursor, ti)
+        recordsProcessed += 1
+      } else if (cmp < 0) {  // si.id < ti.id  ->  copy si
+        let sid = si.id
+        yield queue.push(function *() {
+          let record = yield sr.db(sourceDB).table(table).get(sid).run({timeFormat: 'raw'})
+          yield tr.db(targetDB).table(table).insert(record).run()
+          created += 1
+        })
+        si = yield getNextIdx(sourceCursor, si)
+        recordsProcessed += 1
+      } else if (cmp > 0) {  // si.id > ti.id  ->  delete ti
+        let tid = ti.id
+        ti = yield getNextIdx(targetCursor, ti)
+      } else {
+        console.log(colors.red(`ERROR! Cannot sync, encountered uncomparable PKs`))
+        break
+      }
+    }
+
+    yield tr.db(targetDB).table(table).sync().run()
+  }
+
+  console.log(colors.green(`DONE! Completed in ${startTime.fromNow(true)}`))
+}
+
+var getNextIdx = function *(cursor, idx) {
+  if (idx.id !== Infinity) {
+    try {
+      idx = yield cursor.next()
+    } catch (err) {
+      if (err.message === 'No more rows in the cursor.') {
+        idx = {
+          hash: '',
+          id: Infinity
+        }
+      }
+    }
+  }
+  return idx
+}
diff --git a/lib/main.js b/lib/main.js
index 297045e..a1293e2 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -19,6 +19,7 @@ let HELPTEXT = `
   Commands:
     thinker clone           Clone a database locally or between remote hosts.
     thinker sync            Synchronize differences between two databases.
+    thinker syncinc         Synchronize differences between two databases (without deleting target records).
     thinker -h | --help     Show this screen.
 
 `