Free Practice Questions for LPI 102-500 Exam

The SQL WHERE clause is used to restrict the records that are returned from a SELECT SQL query based on a supplied criteria for the values in the records12. The WHERE clause follows the SELECT and FROM clauses and contains one or more conditions that must be true for a record to be included in the result set. The general syntax of the WHERE clause is:

SELECT column1, column2, ...

FROM table_name

WHERE condition;

The condition can be a comparison, a logical operation, a pattern matching, a subquery, or a combination of these using various operators12. For example, the following query selects all the records from the customers table where the country is ‘USA’:

SELECT * FROM customers

WHERE country = 'USA';

The other words listed in the question are not used to filter records based on values. They have different meanings and purposes in SQL:

CASE: This is a conditional expression that returns a value based on a set of conditions3. It can be used in SELECT, UPDATE, DELETE, or WHERE statements. For example, the following query uses a CASE expression to assign a rating to each customer based on their credit limit:

SELECT customer_name, credit_limit, CASE WHEN credit_limit > 10000 THEN ‘High’ WHEN credit_limit > 5000 THEN ‘Medium’ ELSE ‘Low’ END AS rating FROM customers;

FROM: This is a clause that specifies the table (s) or view (s) from which the data is retrieved. It follows the SELECT clause and precedes the WHERE clause. For example, the following query selects the customer name and order date from the customers and orders tables:

SELECT customer_name, order_date FROM customers JOIN orders ON customers.customer_id = orders.customer_id;

IF: This is a control flow statement that executes a block of code based on a condition. It can be used in stored procedures, functions, triggers, or batch files. For example, the following code snippet uses an IF statement to check if a variable is positive or negative:

DECLARE @num INT; SET @num = -10; IF @num > 0 BEGIN PRINT ‘Positive’; END ELSE BEGIN PRINT ‘Negative’; END

References: 1: SQL WHERE Clause - W3Schools 2: How to Write a WHERE Clause in SQL | LearnSQL.com 3: [SQL CASE Statement - W3Schools] : [SQL FROM Clause - W3Schools] : [SQL IF…ELSE Statement - W3Schools]

In order to run a shell script like a regular command from anywhere in the filesystem, the following requirements must be met:

The script file must be found in the $PATH. The $PATH is a variable that contains a list of directories where the shell looks for executable files when a command is issued. If the script file is not in one of these directories, the shell will not be able to find it unless the full path is specified.

The script file must have the executable permission bit set. This is a file attribute that determines whether the file can be executed by the user, the group, or others. The executable permission bit can be set using the chmod command, for example: chmod +x script.sh.

The script must begin with a shebang-line (#!) that points to the correct interpreter. This is a special line at the beginning of the script that tells the shell which program to use to run the script, such as #!/bin/bash for bash scripts, or #!/usr/bin/perl for perl scripts. The shebang-line must match the exact path of the interpreter, otherwise the script will not run.

The other options are not requirements for running a shell script like a regular command. There is no such group as script, and the file system mount option scripts does not exist. References:

[LPI Linux Essentials - Topic 105: Shells, Scripting and Data Management]

[LPI Linux Professional - Exam 102 Objectives - Topic 105: Shells and Shell Scripting]

(date)"∗∗ComprehensiveExplanation:∗∗Thecorrectwaytoputtheoutputofthecommanddateintotheshellvariablemydateistousecommandsubstitutionwiththesyntax(command). This will execute the command in a subshell and replace the expression with its standard output. The double quotes around the expression will prevent word splitting and globbing of the output. The other options are incorrect because they will either assign a literal string to the variable, use an invalid syntax, or try to execute the command as an arithmetic expression. References:

[LPI Linux Essentials - Topic 105: Shells, Scripting and Data Management]

[LPI Linux Administrator - Exam 102 Objectives - Topic 105: Shells and Shell Scripting]

The correct syntax for selecting specific columns from a table in SQL is to use the SELECT keyword followed by a comma-separated list of column names and then the FROM keyword followed by the table name. Therefore, the only option that follows this syntax is C. SELECT name, address FROM contacts; The other options are incorrect because they either use parentheses around the column names, which are not needed, or they omit the comma between the column names, which causes a syntax error. References: https://www.sqltutorial.org/sql-select/

https://www.w3schools.com/mysql/mysql_select.asp

The while loop reads a line from the standard input and splits it into words using the IFS variable, which by default contains spaces, tabs, and newlines. The read command assigns the first word to the variable a, the second word to the variable b, and the rest of the line to the variable c. Therefore, in this case, a=1, b=2, and c=3 4 5 6. The echo command prints the values of c, b, and a in reverse order, separated by spaces. The output is result: 3 2 1. The loop terminates after reading the first line, since there is no more input to read. References: Bash while Loop | Linuxize, Bash Scripting - While Loop - GeeksforGeeks

The file /etc/profile is a configuration file that is read by the Bash shell when a user logs in. It contains commands and settings that apply to all users of the system, such as environment variables, PATH information, terminal settings, and security commands. Environment variables are variables that affect the behavior of programs and processes. For example, the PATH variable defines the directories where the shell looks for executable files, and the JAVA_HOME variable defines the location of the Java installation. The /etc/profile file can also source other files from the /etc/profile.d/ directory, which can contain additional scripts for setting environment variables or other system-wide settings. The /etc/profile file is not the only file that can set environment variables for a user. There are also user-specific files, such as ~/.profile, ~/.bash_profile, and ~/.bashrc, that are read by the shell after /etc/profile. These files can override or append to the settings in /etc/profile, or define new variables for the user. The order and precedence of these files depend on the type of shell (login or interactive) and the options used to start the shell. You can learn more about the difference between these files here1 and here2. References: https://www.thegeekdiary.com/understanding-etc-profile-configuration-file-in-linux/

https://unix.stackexchange.com/questions/704610/what-does-the-etc-profile-do

In bash, the PID of a shell script’s subshell process is stored in a special variable called $$. This variable is read-only, and you cannot modify it in a shell script1. You can use echo $$ to get the PID of the current bash shell you are using2. Therefore, when the command echo $$ outputs 12942, it means that the PID of the current shell is 12942. References:

[LPI Linux Essentials - Topic 103: Command Line Basics]

[Bash Special Parameters]

How to get the process ID (PID) of a shell script

How to know the process id of current bash session?

The correct keyword for restricting the records that are returned from a SELECT query based on a supplied criteria for the values in the records is WHERE. The WHERE clause is used to filter records based on one or more conditions. The syntax of the WHERE clause is:

SELECT column1, column2, … FROM table_name WHERE condition;

The condition can be a logical expression that evaluates to true, false, or unknown. The condition can also use comparison operators, logical operators, and wildcards to specify the criteria. For example, the following query selects all the records from the employees table where the salary is greater than 50000:

SELECT * FROM employees WHERE salary > 50000;

The other options are incorrect because they have different purposes in SQL:

LIMIT is used to specify the maximum number of records to return from a query. For example, the following query returns only the first 10 records from the employees table:

SELECT * FROM employees LIMIT 10;

FROM is used to specify the table or tables from which to retrieve data. For example, the following query selects all the columns from the employees table:

SELECT * FROM employees;

IF is used to execute a block of code conditionally. For example, the following query updates the salary of an employee based on their performance:

UPDATE employees SET salary = IF(performance = ‘excellent’, salary * 1.1, salary) WHERE employee_id = 123; References: 

https://bing.com/search?q=SQL+statements+restrict+records+based+on+criteria

https://stackoverflow.com/questions/11611931/sql-query-to-select-records-based-on-criteria

The set command is used to display or modify the shell variables and functions in the current shell. When used without any arguments, it prints the names and values of all shell variables, including environment variables and user-defined variables, in alphabetical order. The output also includes the shell options and the positional parameters. The set command can be used in any POSIX-compliant shell, such as bash, zsh, ksh, etc123.

The other options are not correct because:

env is used to print or modify the environment variables, not the shell variables. It does not show the user-defined variables or the shell options. It can also be used to run a command in a modified environment45.

env -a is an invalid option for the env command. The -a option is not supported by the env command in any standard or common implementation45.

echo $ENV is used to print the value of the environment variable ENV, not the list of all shell variables. The ENV variable is usually set to the name of a file that contains commands or aliases to be executed by the shell. It is mainly used by the ksh and some versions of bash .

References: 1: How can I list all shell variables? - Unix & Linux Stack Exchange 2: 2.1 Command Line Basics - Linux Professional Institute Certification … 3: set - The Open Group Base Specifications Issue 7, 2018 edition 4: How to set and list environment variables on Linux 5: env - The Open Group Base Specifications Issue 7, 2018 edition : What is the difference between .bash_profile and .bashrc? - Unix & Linux Stack Exchange : ENV - The Open Group Base Specifications Issue 7, 2018 edition