SQL Exercises: Manager who is supervising 4 or more employees
SQL SUBQUERY: Exercise-50 with Solution
From the following table, write a SQL query to find those managers who supervise four or more employees. Return manager name, department ID.
Sample table : employees+-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+ | EMPLOYEE_ID | FIRST_NAME | LAST_NAME | EMAIL | PHONE_NUMBER | HIRE_DATE | JOB_ID | SALARY | COMMISSION_PCT | MANAGER_ID | DEPARTMENT_ID | +-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+ | 100 | Steven | King | SKING | 515.123.4567 | 2003-06-17 | AD_PRES | 24000.00 | 0.00 | 0 | 90 | | 101 | Neena | Kochhar | NKOCHHAR | 515.123.4568 | 2005-09-21 | AD_VP | 17000.00 | 0.00 | 100 | 90 | | 102 | Lex | De Haan | LDEHAAN | 515.123.4569 | 2001-01-13 | AD_VP | 17000.00 | 0.00 | 100 | 90 | | 103 | Alexander | Hunold | AHUNOLD | 590.423.4567 | 2006-01-03 | IT_PROG | 9000.00 | 0.00 | 102 | 60 | | 104 | Bruce | Ernst | BERNST | 590.423.4568 | 2007-05-21 | IT_PROG | 6000.00 | 0.00 | 103 | 60 | | 105 | David | Austin | DAUSTIN | 590.423.4569 | 2005-06-25 | IT_PROG | 4800.00 | 0.00 | 103 | 60 | | 106 | Valli | Pataballa | VPATABAL | 590.423.4560 | 2006-02-05 | IT_PROG | 4800.00 | 0.00 | 103 | 60 | | 107 | Diana | Lorentz | DLORENTZ | 590.423.5567 | 2007-02-07 | IT_PROG | 4200.00 | 0.00 | 103 | 60 | | 108 | Nancy | Greenberg | NGREENBE | 515.124.4569 | 2002-08-17 | FI_MGR | 12008.00 | 0.00 | 101 | 100 | | 109 | Daniel | Faviet | DFAVIET | 515.124.4169 | 2002-08-16 | FI_ACCOUNT | 9000.00 | 0.00 | 108 | 100 | | 110 | John | Chen | JCHEN | 515.124.4269 | 2005-09-28 | FI_ACCOUNT | 8200.00 | 0.00 | 108 | 100 | | 111 | Ismael | Sciarra | ISCIARRA | 515.124.4369 | 2005-09-30 | FI_ACCOUNT | 7700.00 | 0.00 | 108 | 100 | | 112 | Jose Manuel | Urman | JMURMAN | 515.124.4469 | 2006-03-07 | FI_ACCOUNT | 7800.00 | 0.00 | 108 | 100 | | 113 | Luis | Popp | LPOPP | 515.124.4567 | 2007-12-07 | FI_ACCOUNT | 6900.00 | 0.00 | 108 | 100 | | 114 | Den | Raphaely | DRAPHEAL | 515.127.4561 | 2002-12-07 | PU_MAN | 11000.00 | 0.00 | 100 | 30 | | 115 | Alexander | Khoo | AKHOO | 515.127.4562 | 2003-05-18 | PU_CLERK | 3100.00 | 0.00 | 114 | 30 | | 116 | Shelli | Baida | SBAIDA | 515.127.4563 | 2005-12-24 | PU_CLERK | 2900.00 | 0.00 | 114 | 30 | | 117 | Sigal | Tobias | STOBIAS | 515.127.4564 | 2005-07-24 | PU_CLERK | 2800.00 | 0.00 | 114 | 30 | | 118 | Guy | Himuro | GHIMURO | 515.127.4565 | 2006-11-15 | PU_CLERK | 2600.00 | 0.00 | 114 | 30 | | 119 | Karen | Colmenares | KCOLMENA | 515.127.4566 | 2007-08-10 | PU_CLERK | 2500.00 | 0.00 | 114 | 30 | | 120 | Matthew | Weiss | MWEISS | 650.123.1234 | 2004-07-18 | ST_MAN | 8000.00 | 0.00 | 100 | 50 | | 121 | Adam | Fripp | AFRIPP | 650.123.2234 | 2005-04-10 | ST_MAN | 8200.00 | 0.00 | 100 | 50 | | 122 | Payam | Kaufling | PKAUFLIN | 650.123.3234 | 2003-05-01 | ST_MAN | 7900.00 | 0.00 | 100 | 50 | | 123 | Shanta | Vollman | SVOLLMAN | 650.123.4234 | 2005-10-10 | ST_MAN | 6500.00 | 0.00 | 100 | 50 | | 124 | Kevin | Mourgos | KMOURGOS | 650.123.5234 | 2007-11-16 | ST_MAN | 5800.00 | 0.00 | 100 | 50 | | 125 | Julia | Nayer | JNAYER | 650.124.1214 | 2005-07-16 | ST_CLERK | 3200.00 | 0.00 | 120 | 50 | | 126 | Irene | Mikkilineni | IMIKKILI | 650.124.1224 | 2006-09-28 | ST_CLERK | 2700.00 | 0.00 | 120 | 50 | | 127 | James | Landry | JLANDRY | 650.124.1334 | 2007-01-14 | ST_CLERK | 2400.00 | 0.00 | 120 | 50 | | 128 | Steven | Markle | SMARKLE | 650.124.1434 | 2008-03-08 | ST_CLERK | 2200.00 | 0.00 | 120 | 50 | | 129 | Laura | Bissot | LBISSOT | 650.124.5234 | 2005-08-20 | ST_CLERK | 3300.00 | 0.00 | 121 | 50 | | 130 | Mozhe | Atkinson | MATKINSO | 650.124.6234 | 2005-10-30 | ST_CLERK | 2800.00 | 0.00 | 121 | 50 | | 131 | James | Marlow | JAMRLOW | 650.124.7234 | 2005-02-16 | ST_CLERK | 2500.00 | 0.00 | 121 | 50 | | 132 | TJ | Olson | TJOLSON | 650.124.8234 | 2007-04-10 | ST_CLERK | 2100.00 | 0.00 | 121 | 50 | | 133 | Jason | Mallin | JMALLIN | 650.127.1934 | 2004-06-14 | ST_CLERK | 3300.00 | 0.00 | 122 | 50 | | 134 | Michael | Rogers | MROGERS | 650.127.1834 | 2006-08-26 | ST_CLERK | 2900.00 | 0.00 | 122 | 50 | | 135 | Ki | Gee | KGEE | 650.127.1734 | 2007-12-12 | ST_CLERK | 2400.00 | 0.00 | 122 | 50 | | 136 | Hazel | Philtanker | HPHILTAN | 650.127.1634 | 2008-02-06 | ST_CLERK | 2200.00 | 0.00 | 122 | 50 | | 137 | Renske | Ladwig | RLADWIG | 650.121.1234 | 2003-07-14 | ST_CLERK | 3600.00 | 0.00 | 123 | 50 | | 138 | Stephen | Stiles | SSTILES | 650.121.2034 | 2005-10-26 | ST_CLERK | 3200.00 | 0.00 | 123 | 50 | | 139 | John | Seo | JSEO | 650.121.2019 | 2006-02-12 | ST_CLERK | 2700.00 | 0.00 | 123 | 50 | | 140 | Joshua | Patel | JPATEL | 650.121.1834 | 2006-04-06 | ST_CLERK | 2500.00 | 0.00 | 123 | 50 | | 141 | Trenna | Rajs | TRAJS | 650.121.8009 | 2003-10-17 | ST_CLERK | 3500.00 | 0.00 | 124 | 50 | | 142 | Curtis | Davies | CDAVIES | 650.121.2994 | 2005-01-29 | ST_CLERK | 3100.00 | 0.00 | 124 | 50 | | 143 | Randall | Matos | RMATOS | 650.121.2874 | 2006-03-15 | ST_CLERK | 2600.00 | 0.00 | 124 | 50 | | 144 | Peter | Vargas | PVARGAS | 650.121.2004 | 2006-07-09 | ST_CLERK | 2500.00 | 0.00 | 124 | 50 | | 145 | John | Russell | JRUSSEL | 011.44.1344.429268 | 2004-10-01 | SA_MAN | 14000.00 | 0.40 | 100 | 80 | | 146 | Karen | Partners | KPARTNER | 011.44.1344.467268 | 2005-01-05 | SA_MAN | 13500.00 | 0.30 | 100 | 80 | | 147 | Alberto | Errazuriz | AERRAZUR | 011.44.1344.429278 | 2005-03-10 | SA_MAN | 12000.00 | 0.30 | 100 | 80 | | 148 | Gerald | Cambrault | GCAMBRAU | 011.44.1344.619268 | 2007-10-15 | SA_MAN | 11000.00 | 0.30 | 100 | 80 | | 149 | Eleni | Zlotkey | EZLOTKEY | 011.44.1344.429018 | 2008-01-29 | SA_MAN | 10500.00 | 0.20 | 100 | 80 | | 150 | Peter | Tucker | PTUCKER | 011.44.1344.129268 | 2005-01-30 | SA_REP | 10000.00 | 0.30 | 145 | 80 | | 151 | David | Bernstein | DBERNSTE | 011.44.1344.345268 | 2005-03-24 | SA_REP | 9500.00 | 0.25 | 145 | 80 | | 152 | Peter | Hall | PHALL | 011.44.1344.478968 | 2005-08-20 | SA_REP | 9000.00 | 0.25 | 145 | 80 | | 153 | Christopher | Olsen | COLSEN | 011.44.1344.498718 | 2006-03-30 | SA_REP | 8000.00 | 0.20 | 145 | 80 | | 154 | Nanette | Cambrault | NCAMBRAU | 011.44.1344.987668 | 2006-12-09 | SA_REP | 7500.00 | 0.20 | 145 | 80 | | 155 | Oliver | Tuvault | OTUVAULT | 011.44.1344.486508 | 2007-11-23 | SA_REP | 7000.00 | 0.15 | 145 | 80 | | 156 | Janette | King | JKING | 011.44.1345.429268 | 2004-01-30 | SA_REP | 10000.00 | 0.35 | 146 | 80 | | 157 | Patrick | Sully | PSULLY | 011.44.1345.929268 | 2004-03-04 | SA_REP | 9500.00 | 0.35 | 146 | 80 | | 158 | Allan | McEwen | AMCEWEN | 011.44.1345.829268 | 2004-08-01 | SA_REP | 9000.00 | 0.35 | 146 | 80 | | 159 | Lindsey | Smith | LSMITH | 011.44.1345.729268 | 2005-03-10 | SA_REP | 8000.00 | 0.30 | 146 | 80 | | 160 | Louise | Doran | LDORAN | 011.44.1345.629268 | 2005-12-15 | SA_REP | 7500.00 | 0.30 | 146 | 80 | | 161 | Sarath | Sewall | SSEWALL | 011.44.1345.529268 | 2006-11-03 | SA_REP | 7000.00 | 0.25 | 146 | 80 | | 162 | Clara | Vishney | CVISHNEY | 011.44.1346.129268 | 2005-11-11 | SA_REP | 10500.00 | 0.25 | 147 | 80 | | 163 | Danielle | Greene | DGREENE | 011.44.1346.229268 | 2007-03-19 | SA_REP | 9500.00 | 0.15 | 147 | 80 | | 164 | Mattea | Marvins | MMARVINS | 011.44.1346.329268 | 2008-01-24 | SA_REP | 7200.00 | 0.10 | 147 | 80 | | 165 | David | Lee | DLEE | 011.44.1346.529268 | 2008-02-23 | SA_REP | 6800.00 | 0.10 | 147 | 80 | | 166 | Sundar | Ande | SANDE | 011.44.1346.629268 | 2008-03-24 | SA_REP | 6400.00 | 0.10 | 147 | 80 | | 167 | Amit | Banda | ABANDA | 011.44.1346.729268 | 2008-04-21 | SA_REP | 6200.00 | 0.10 | 147 | 80 | | 168 | Lisa | Ozer | LOZER | 011.44.1343.929268 | 2005-03-11 | SA_REP | 11500.00 | 0.25 | 148 | 80 | | 169 | Harrison | Bloom | HBLOOM | 011.44.1343.829268 | 2006-03-23 | SA_REP | 10000.00 | 0.20 | 148 | 80 | | 170 | Tayler | Fox | TFOX | 011.44.1343.729268 | 2006-01-24 | SA_REP | 9600.00 | 0.20 | 148 | 80 | | 171 | William | Smith | WSMITH | 011.44.1343.629268 | 2007-02-23 | SA_REP | 7400.00 | 0.15 | 148 | 80 | | 172 | Elizabeth | Bates | EBATES | 011.44.1343.529268 | 2007-03-24 | SA_REP | 7300.00 | 0.15 | 148 | 80 | | 173 | Sundita | Kumar | SKUMAR | 011.44.1343.329268 | 2008-04-21 | SA_REP | 6100.00 | 0.10 | 148 | 80 | | 174 | Ellen | Abel | EABEL | 011.44.1644.429267 | 2004-05-11 | SA_REP | 11000.00 | 0.30 | 149 | 80 | | 175 | Alyssa | Hutton | AHUTTON | 011.44.1644.429266 | 2005-03-19 | SA_REP | 8800.00 | 0.25 | 149 | 80 | | 176 | Jonathon | Taylor | JTAYLOR | 011.44.1644.429265 | 2006-03-24 | SA_REP | 8600.00 | 0.20 | 149 | 80 | | 177 | Jack | Livingston | JLIVINGS | 011.44.1644.429264 | 2006-04-23 | SA_REP | 8400.00 | 0.20 | 149 | 80 | | 178 | Kimberely | Grant | KGRANT | 011.44.1644.429263 | 2007-05-24 | SA_REP | 7000.00 | 0.15 | 149 | 0 | | 179 | Charles | Johnson | CJOHNSON | 011.44.1644.429262 | 2008-01-04 | SA_REP | 6200.00 | 0.10 | 149 | 80 | | 180 | Winston | Taylor | WTAYLOR | 650.507.9876 | 2006-01-24 | SH_CLERK | 3200.00 | 0.00 | 120 | 50 | | 181 | Jean | Fleaur | JFLEAUR | 650.507.9877 | 2006-02-23 | SH_CLERK | 3100.00 | 0.00 | 120 | 50 | | 182 | Martha | Sullivan | MSULLIVA | 650.507.9878 | 2007-06-21 | SH_CLERK | 2500.00 | 0.00 | 120 | 50 | | 183 | Girard | Geoni | GGEONI | 650.507.9879 | 2008-02-03 | SH_CLERK | 2800.00 | 0.00 | 120 | 50 | | 184 | Nandita | Sarchand | NSARCHAN | 650.509.1876 | 2004-01-27 | SH_CLERK | 4200.00 | 0.00 | 121 | 50 | | 185 | Alexis | Bull | ABULL | 650.509.2876 | 2005-02-20 | SH_CLERK | 4100.00 | 0.00 | 121 | 50 | | 186 | Julia | Dellinger | JDELLING | 650.509.3876 | 2006-06-24 | SH_CLERK | 3400.00 | 0.00 | 121 | 50 | | 187 | Anthony | Cabrio | ACABRIO | 650.509.4876 | 2007-02-07 | SH_CLERK | 3000.00 | 0.00 | 121 | 50 | | 188 | Kelly | Chung | KCHUNG | 650.505.1876 | 2005-06-14 | SH_CLERK | 3800.00 | 0.00 | 122 | 50 | | 189 | Jennifer | Dilly | JDILLY | 650.505.2876 | 2005-08-13 | SH_CLERK | 3600.00 | 0.00 | 122 | 50 | | 190 | Timothy | Gates | TGATES | 650.505.3876 | 2006-07-11 | SH_CLERK | 2900.00 | 0.00 | 122 | 50 | | 191 | Randall | Perkins | RPERKINS | 650.505.4876 | 2007-12-19 | SH_CLERK | 2500.00 | 0.00 | 122 | 50 | | 192 | Sarah | Bell | SBELL | 650.501.1876 | 2004-02-04 | SH_CLERK | 4000.00 | 0.00 | 123 | 50 | | 193 | Britney | Everett | BEVERETT | 650.501.2876 | 2005-03-03 | SH_CLERK | 3900.00 | 0.00 | 123 | 50 | | 194 | Samuel | McCain | SMCCAIN | 650.501.3876 | 2006-07-01 | SH_CLERK | 3200.00 | 0.00 | 123 | 50 | | 195 | Vance | Jones | VJONES | 650.501.4876 | 2007-03-17 | SH_CLERK | 2800.00 | 0.00 | 123 | 50 | | 196 | Alana | Walsh | AWALSH | 650.507.9811 | 2006-04-24 | SH_CLERK | 3100.00 | 0.00 | 124 | 50 | | 197 | Kevin | Feeney | KFEENEY | 650.507.9822 | 2006-05-23 | SH_CLERK | 3000.00 | 0.00 | 124 | 50 | | 198 | Donald | OConnell | DOCONNEL | 650.507.9833 | 2007-06-21 | SH_CLERK | 2600.00 | 0.00 | 124 | 50 | | 199 | Douglas | Grant | DGRANT | 650.507.9844 | 2008-01-13 | SH_CLERK | 2600.00 | 0.00 | 124 | 50 | | 200 | Jennifer | Whalen | JWHALEN | 515.123.4444 | 2003-09-17 | AD_ASST | 4400.00 | 0.00 | 101 | 10 | | 201 | Michael | Hartstein | MHARTSTE | 515.123.5555 | 2004-02-17 | MK_MAN | 13000.00 | 0.00 | 100 | 20 | | 202 | Pat | Fay | PFAY | 603.123.6666 | 2005-08-17 | MK_REP | 6000.00 | 0.00 | 201 | 20 | | 203 | Susan | Mavris | SMAVRIS | 515.123.7777 | 2002-06-07 | HR_REP | 6500.00 | 0.00 | 101 | 40 | | 204 | Hermann | Baer | HBAER | 515.123.8888 | 2002-06-07 | PR_REP | 10000.00 | 0.00 | 101 | 70 | | 205 | Shelley | Higgins | SHIGGINS | 515.123.8080 | 2002-06-07 | AC_MGR | 12008.00 | 0.00 | 101 | 110 | | 206 | William | Gietz | WGIETZ | 515.123.8181 | 2002-06-07 | AC_ACCOUNT | 8300.00 | 0.00 | 205 | 110 | +-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+
Sample Solution:
-- Selecting a concatenated string of 'first_name' and 'last_name' as 'Manager_name', and the 'department_id' from the 'employees' table
SELECT first_name || ' ' || last_name AS Manager_name, department_id
-- Filtering rows based on the condition that the 'employee_id' is in the result set of a subquery
FROM employees
-- Subquery to find 'manager_id' values where the count of occurrences is greater than or equal to 4 in the 'employees' table
WHERE employee_id IN
( SELECT manager_id
FROM employees
-- Grouping 'manager_id' values and filtering based on the count of occurrences
GROUP BY manager_id
HAVING COUNT(*) >= 4
);
Sample Output:
manager_name department_id Steven King 90 Neena Kochhar 90 Alexander Hunold 60 Nancy Greenberg 100 Den Raphaely 30 Matthew Weiss 50 Adam Fripp 50 Payam Kaufling 50 Shanta Vollman 50 Kevin Mourgos 50 John Russell 80 Karen Partners 80 Alberto Errazuriz 80 Gerald Cambrault 80 Eleni Zlotkey 80
Code Explanation:
The said query in SQL that selects the names of employees who are managers and have at least 4 employees reporting to them, along with the department IDs of their respective departments. The "||" symbol concatenates the first name, a space, and the last name of each employee to create the Manager_name field. The query first uses a subquery to identify the manager IDs that meet the condition of having at least 4 direct reports.
Visual Presentation:
Alternative Solutions:
Using EXISTS:
SELECT e1.first_name || ' ' || e1.last_name AS Manager_name, e1.department_id
FROM employees e1
WHERE EXISTS (
SELECT 1
FROM employees e2
WHERE e2.manager_id = e1.employee_id
GROUP BY e2.manager_id
HAVING COUNT(*) >= 4
);
Using JOINs:
SELECT DISTINCT e1.first_name || ' ' || e1.last_name AS Manager_name, e1.department_id
FROM employees e1
JOIN employees e2 ON e1.employee_id = e2.manager_id
GROUP BY e1.employee_id, e1.first_name, e1.last_name, e1.department_id
HAVING COUNT(*) >= 4;
Using a Scalar Subquery in the WHERE Clause:
SELECT first_name || ' ' || last_name AS Manager_name, department_id
FROM employees
WHERE employee_id IN (
SELECT DISTINCT manager_id
FROM employees
GROUP BY manager_id
HAVING COUNT(*) >= 4
);
Practice Online
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