Notebooks/06.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Relational Algebra\n",
    "---\n",
    "\n",
    "`Relational algebra` is a `procedural query language`, which takes instances of relations as input and yields instances of relations as output. It uses operators to perform queries. An `operator` can be either unary or binary. They accept relations as their input and yield relations as their output."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Connecting with the database"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "%load_ext sql\n",
    "# replace with your own credentials\n",
    "%sql ibm_db_sa://my-username:my-password@dashdb-txn-sbox-yp-dal09-03.services.dal.bluemix.net:50000/BLUDB"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### • <u>SELECT</u>\n",
    "it is used to select the subset of the tuples of a relation that satisfies the selection condition."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " * ibm_db_sa://lzv55210:***@dashdb-txn-sbox-yp-dal09-12.services.dal.bluemix.net:50000/BLUDB\n",
      "Done.\n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<table>\n",
       "    <tr>\n",
       "        <th>country</th>\n",
       "        <th>first_name</th>\n",
       "        <th>last_name</th>\n",
       "        <th>test_score</th>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>United States</td>\n",
       "        <td>Marshall</td>\n",
       "        <td>Bernadot</td>\n",
       "        <td>54</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>United States</td>\n",
       "        <td>Celinda</td>\n",
       "        <td>Malkin</td>\n",
       "        <td>51</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Ukraine</td>\n",
       "        <td>Guillermo</td>\n",
       "        <td>Furze</td>\n",
       "        <td>53</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Ukraine</td>\n",
       "        <td>Aharon</td>\n",
       "        <td>Tunnow</td>\n",
       "        <td>48</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Russia</td>\n",
       "        <td>Bail</td>\n",
       "        <td>Goodwin</td>\n",
       "        <td>46</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Poland</td>\n",
       "        <td>Cole</td>\n",
       "        <td>Winteringham</td>\n",
       "        <td>49</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Sweden</td>\n",
       "        <td>Emlyn</td>\n",
       "        <td>Erricker</td>\n",
       "        <td>55</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Russia</td>\n",
       "        <td>Cathee</td>\n",
       "        <td>Sivewright</td>\n",
       "        <td>49</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Poland</td>\n",
       "        <td>Barny</td>\n",
       "        <td>Ingerson</td>\n",
       "        <td>57</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Sweden</td>\n",
       "        <td>Sharla</td>\n",
       "        <td>Papaccio</td>\n",
       "        <td>55</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Romania</td>\n",
       "        <td>Alina</td>\n",
       "        <td>Smolyar</td>\n",
       "        <td>52</td>\n",
       "    </tr>\n",
       "</table>"
      ],
      "text/plain": [
       "[('United States', 'Marshall', 'Bernadot', 54),\n",
       " ('United States', 'Celinda', 'Malkin', 51),\n",
       " ('Ukraine', 'Guillermo', 'Furze', 53),\n",
       " ('Ukraine', 'Aharon', 'Tunnow', 48),\n",
       " ('Russia', 'Bail', 'Goodwin', 46),\n",
       " ('Poland', 'Cole', 'Winteringham', 49),\n",
       " ('Sweden', 'Emlyn', 'Erricker', 55),\n",
       " ('Russia', 'Cathee', 'Sivewright', 49),\n",
       " ('Poland', 'Barny', 'Ingerson', 57),\n",
       " ('Sweden', 'Sharla', 'Papaccio', 55),\n",
       " ('Romania', 'Alina', 'Smolyar', 52)]"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%sql select * from STUDENTS"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### • <u>PROJECT</u>\n",
    "It selects only those columns or attributes in which the user is intersted."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " * ibm_db_sa://lzv55210:***@dashdb-txn-sbox-yp-dal09-12.services.dal.bluemix.net:50000/BLUDB\n",
      "Done.\n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<table>\n",
       "    <tr>\n",
       "        <th>first_name</th>\n",
       "        <th>test_score</th>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Marshall</td>\n",
       "        <td>54</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Celinda</td>\n",
       "        <td>51</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Guillermo</td>\n",
       "        <td>53</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Aharon</td>\n",
       "        <td>48</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Bail</td>\n",
       "        <td>46</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Cole</td>\n",
       "        <td>49</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Emlyn</td>\n",
       "        <td>55</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Cathee</td>\n",
       "        <td>49</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Barny</td>\n",
       "        <td>57</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Sharla</td>\n",
       "        <td>55</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Alina</td>\n",
       "        <td>52</td>\n",
       "    </tr>\n",
       "</table>"
      ],
      "text/plain": [
       "[('Marshall', 54),\n",
       " ('Celinda', 51),\n",
       " ('Guillermo', 53),\n",
       " ('Aharon', 48),\n",
       " ('Bail', 46),\n",
       " ('Cole', 49),\n",
       " ('Emlyn', 55),\n",
       " ('Cathee', 49),\n",
       " ('Barny', 57),\n",
       " ('Sharla', 55),\n",
       " ('Alina', 52)]"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%sql select first_name,test_score from STUDENTS"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### • <u>SET OPERATIONS</u>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Lets make another table since we'll need two tables in the following operations."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " * ibm_db_sa://lzv55210:***@dashdb-txn-sbox-yp-dal09-12.services.dal.bluemix.net:50000/BLUDB\n",
      "Done.\n",
      "Done.\n",
      "4 rows affected.\n",
      "Done.\n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<table>\n",
       "    <tr>\n",
       "        <th>country</th>\n",
       "        <th>first_name</th>\n",
       "        <th>last_name</th>\n",
       "        <th>test_score</th>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Mexico</td>\n",
       "        <td>Natasha</td>\n",
       "        <td>Martinax</td>\n",
       "        <td>48</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Mexico</td>\n",
       "        <td>Rachael</td>\n",
       "        <td>Grate</td>\n",
       "        <td>45</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Romania</td>\n",
       "        <td>Alexandra</td>\n",
       "        <td>Botez</td>\n",
       "        <td>57</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Romania</td>\n",
       "        <td>Alina</td>\n",
       "        <td>Smolyar</td>\n",
       "        <td>52</td>\n",
       "    </tr>\n",
       "</table>"
      ],
      "text/plain": [
       "[('Mexico', 'Natasha', 'Martinax', 48),\n",
       " ('Mexico', 'Rachael', 'Grate', 45),\n",
       " ('Romania', 'Alexandra', 'Botez', 57),\n",
       " ('Romania', 'Alina', 'Smolyar', 52)]"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%%sql\n",
    "\n",
    "drop table NEW_STUDENTS;\n",
    "create table NEW_STUDENTS (\n",
    "\tcountry VARCHAR(50),\n",
    "\tfirst_name VARCHAR(50),\n",
    "\tlast_name VARCHAR(50),\n",
    "\ttest_score INT\n",
    ");\n",
    "insert into NEW_STUDENTS (country, first_name, last_name, test_score)\n",
    "values\n",
    "('Mexico', 'Natasha', 'Martinax', 48),\n",
    "('Mexico', 'Rachael', 'Grate', 45),\n",
    "('Romania', 'Alexandra', 'Botez', 57),\n",
    "('Romania', 'Alina', 'Smolyar', 52);\n",
    "select * from NEW_STUDENTS"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 1. UNION\n",
    "It is used to combine the results of two or more select statements. However it will eliminate duplicate rows from its result set. In case of union, number of columns and data type must be saame in all the tables."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " * ibm_db_sa://lzv55210:***@dashdb-txn-sbox-yp-dal09-12.services.dal.bluemix.net:50000/BLUDB\n",
      "Done.\n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<table>\n",
       "    <tr>\n",
       "        <th>country</th>\n",
       "        <th>first_name</th>\n",
       "        <th>last_name</th>\n",
       "        <th>test_score</th>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Mexico</td>\n",
       "        <td>Rachael</td>\n",
       "        <td>Grate</td>\n",
       "        <td>45</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Russia</td>\n",
       "        <td>Bail</td>\n",
       "        <td>Goodwin</td>\n",
       "        <td>46</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Mexico</td>\n",
       "        <td>Natasha</td>\n",
       "        <td>Martinax</td>\n",
       "        <td>48</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Ukraine</td>\n",
       "        <td>Aharon</td>\n",
       "        <td>Tunnow</td>\n",
       "        <td>48</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Russia</td>\n",
       "        <td>Cathee</td>\n",
       "        <td>Sivewright</td>\n",
       "        <td>49</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Poland</td>\n",
       "        <td>Cole</td>\n",
       "        <td>Winteringham</td>\n",
       "        <td>49</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>United States</td>\n",
       "        <td>Celinda</td>\n",
       "        <td>Malkin</td>\n",
       "        <td>51</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Romania</td>\n",
       "        <td>Alina</td>\n",
       "        <td>Smolyar</td>\n",
       "        <td>52</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Ukraine</td>\n",
       "        <td>Guillermo</td>\n",
       "        <td>Furze</td>\n",
       "        <td>53</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>United States</td>\n",
       "        <td>Marshall</td>\n",
       "        <td>Bernadot</td>\n",
       "        <td>54</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Sweden</td>\n",
       "        <td>Emlyn</td>\n",
       "        <td>Erricker</td>\n",
       "        <td>55</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Sweden</td>\n",
       "        <td>Sharla</td>\n",
       "        <td>Papaccio</td>\n",
       "        <td>55</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Romania</td>\n",
       "        <td>Alexandra</td>\n",
       "        <td>Botez</td>\n",
       "        <td>57</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Poland</td>\n",
       "        <td>Barny</td>\n",
       "        <td>Ingerson</td>\n",
       "        <td>57</td>\n",
       "    </tr>\n",
       "</table>"
      ],
      "text/plain": [
       "[('Mexico', 'Rachael', 'Grate', 45),\n",
       " ('Russia', 'Bail', 'Goodwin', 46),\n",
       " ('Mexico', 'Natasha', 'Martinax', 48),\n",
       " ('Ukraine', 'Aharon', 'Tunnow', 48),\n",
       " ('Russia', 'Cathee', 'Sivewright', 49),\n",
       " ('Poland', 'Cole', 'Winteringham', 49),\n",
       " ('United States', 'Celinda', 'Malkin', 51),\n",
       " ('Romania', 'Alina', 'Smolyar', 52),\n",
       " ('Ukraine', 'Guillermo', 'Furze', 53),\n",
       " ('United States', 'Marshall', 'Bernadot', 54),\n",
       " ('Sweden', 'Emlyn', 'Erricker', 55),\n",
       " ('Sweden', 'Sharla', 'Papaccio', 55),\n",
       " ('Romania', 'Alexandra', 'Botez', 57),\n",
       " ('Poland', 'Barny', 'Ingerson', 57)]"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%sql select * from STUDENTS union select * from NEW_STUDENTS"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 2. INTERSECTION\n",
    "It returna the rows which are common in both the tables."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " * ibm_db_sa://lzv55210:***@dashdb-txn-sbox-yp-dal09-12.services.dal.bluemix.net:50000/BLUDB\n",
      "Done.\n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<table>\n",
       "    <tr>\n",
       "        <th>country</th>\n",
       "        <th>first_name</th>\n",
       "        <th>last_name</th>\n",
       "        <th>test_score</th>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Romania</td>\n",
       "        <td>Alina</td>\n",
       "        <td>Smolyar</td>\n",
       "        <td>52</td>\n",
       "    </tr>\n",
       "</table>"
      ],
      "text/plain": [
       "[('Romania', 'Alina', 'Smolyar', 52)]"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%sql select * from STUDENTS intersect select * from NEW_STUDENTS"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 3. DIFFERENCE\n",
    "It combines the result of two select staements and returns only those rows which belongs to first set of result."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " * ibm_db_sa://lzv55210:***@dashdb-txn-sbox-yp-dal09-12.services.dal.bluemix.net:50000/BLUDB\n",
      "Done.\n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<table>\n",
       "    <tr>\n",
       "        <th>country</th>\n",
       "        <th>first_name</th>\n",
       "        <th>last_name</th>\n",
       "        <th>test_score</th>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>United States</td>\n",
       "        <td>Marshall</td>\n",
       "        <td>Bernadot</td>\n",
       "        <td>54</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>United States</td>\n",
       "        <td>Celinda</td>\n",
       "        <td>Malkin</td>\n",
       "        <td>51</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Ukraine</td>\n",
       "        <td>Guillermo</td>\n",
       "        <td>Furze</td>\n",
       "        <td>53</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Ukraine</td>\n",
       "        <td>Aharon</td>\n",
       "        <td>Tunnow</td>\n",
       "        <td>48</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Russia</td>\n",
       "        <td>Bail</td>\n",
       "        <td>Goodwin</td>\n",
       "        <td>46</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Poland</td>\n",
       "        <td>Cole</td>\n",
       "        <td>Winteringham</td>\n",
       "        <td>49</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Sweden</td>\n",
       "        <td>Emlyn</td>\n",
       "        <td>Erricker</td>\n",
       "        <td>55</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Russia</td>\n",
       "        <td>Cathee</td>\n",
       "        <td>Sivewright</td>\n",
       "        <td>49</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Poland</td>\n",
       "        <td>Barny</td>\n",
       "        <td>Ingerson</td>\n",
       "        <td>57</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "        <td>Sweden</td>\n",
       "        <td>Sharla</td>\n",
       "        <td>Papaccio</td>\n",
       "        <td>55</td>\n",
       "    </tr>\n",
       "</table>"
      ],
      "text/plain": [
       "[('United States', 'Marshall', 'Bernadot', 54),\n",
       " ('United States', 'Celinda', 'Malkin', 51),\n",
       " ('Ukraine', 'Guillermo', 'Furze', 53),\n",
       " ('Ukraine', 'Aharon', 'Tunnow', 48),\n",
       " ('Russia', 'Bail', 'Goodwin', 46),\n",
       " ('Poland', 'Cole', 'Winteringham', 49),\n",
       " ('Sweden', 'Emlyn', 'Erricker', 55),\n",
       " ('Russia', 'Cathee', 'Sivewright', 49),\n",
       " ('Poland', 'Barny', 'Ingerson', 57),\n",
       " ('Sweden', 'Sharla', 'Papaccio', 55)]"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%sql select STUDENTS.* from STUDENTS where STUDENTS.first_name not in ( select first_name from NEW_STUDENTS )"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Thanks for reading :)\n",
    "Created by [Tarun Kamboj](https://www.linkedin.com/in/kambojtarun/)."
   ]
  }
 ],
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