Coding and Problem-solving Skills are essential for delivering high quality software applications. Some of the good practises are as follows:

 1. Modular and Efficient code (Reuse code by writing common functions). This helps in code optimization.

 2. Null checks (guard clause for validation check null and return), proper variable names, null & length check, set default values wherever possible.

 3. Memory handling needs to be done in code in case of C programming.

 4. Initialize/Reset variables in case of nested while loops.

 5. Write Code Comments, makes easy to read code & understand the logic. Helps in maintaining and keeping code defect free.

 6. Make code configurable for attributes whose values might change.

 7. Refering cache in order to reduce database calls for better performance.

 8. Code reviews by Peers. This makes us learn from each other and improve our skills.

 9. Analysing log files to troubleshoot issues.

 10. Happy Coding. Write great code and use great languages.

 Other tips include:

Function Name	Details
strcmp()	compares two strings and returns zero if they are identical.
strstr()	useful for searching and extracting substrings within larger strings!
sprintf()	formats and stores output in a character string buffer.
sscanf()	reads formatted input from a string in the provided variables.
strcpy()	copies a string from one location to another.
strlen()	calculates the length of a given string (excluding the null character).
localtime()	converts time_t variable to a structure of type tm.
mktime()	converts structure of type tm to a time_t variable.
strptime()	converts time stored in string variable to struct tm variable (according to the given string format).
strftime()	converts struct tm variable to string for printing to log for debugging.
atoi_64()	converts string to numeric value.
malloc()	dynamically allocates memory on the heap.
free()	deallocates memory previously allocated by malloc().Helps prevent memory leaks by releasing unused memory.

 Code snippets for strcmp(), sprintf():
if(str1 && str2 && strcmp(str1, str2) == 0)
{
sprintf(printbuff, "str1 and str2 Strings are same and values are %s and %s\n", str1, str2);
}

strstr() & sscanf():
if(str1 && str2 && strstr(str1, str2) != NULL) {
sprintf(printfbuff, "str2 is present in str1\n");
sscanf(str1, "%2d", strmmdd); //read first 2 characters from str1 into integer variable strmmdd
}

 The struct tm represents date and time information. Used for manipulating and formatting time-related data.

time_t epoch_time = <time-unixtimestamp>
struct tm new_tm = localtime(&epoch_time); //store unix timestamp "epoch_time" into struct tm variable "new_tm"

//Adjust new_tm
new_tm->tm_mon = <month>;
new_tm->tm_year = <year>;
new_tm->tm_mday = <dayofmonth>;
new_tm->tm_hour = 0;
new_tm->tm_min = 0;
new_tm->tm_sec = 0;
new_tm->tm_isdst = -1;
time_t new_unixtime = mktime(&new_tm); //convert struct tm variable into unixtimestamp epoch variable

Annotations help in avoid writing bolierplate code and improves coding efficiency. Below are some common Java Annotations:

Annotation Name	Details
@Autowired	Facilitates dependency injection, automatically injecting Spring beans into your classes without explicit instantiation
@Override	Overrides the default implementation
@LogExecutionTime	Logs time take in execution of function
@Component	Designates a Java class as a Spring-managed component
@Slf4j	Logging annotation for Spring Boot applications
@Repository	Indicate that a class is a Data Access Object (DAO) or repository, signifying its role in interacting with the database
@Entity	To treat a Java class as a persistent entity, making it easier to perform database operations
@Getter @Setter	Creates Getter and Setter functions automatically without explicitly defining them
@ToString	Current state of the object will be returned as a String when toString() will be called
@Id	Spring Data JPA – @Id Annotation, used to mark a field as the primary key of an entity

Note: Lombok is a Java library that can generate known patterns of code for us, allowing us to reduce the boilerplate code.

Search string/pattern using grep commands:

grep Command	Details
grep -n "string" <filename>	search string with line numbers displayed
grep -i "string" <filename>	case insensitive search
grep -r "string"	recursive search in folders/sub folders
grep -E -w "Enter|Exit" <filename>	w word match, E regular expression
grep "lines.*empty" <filename>	searches all patterns that starts with “lines” and ends with “empty” with anything in-between
grep -A <N> "string" <filename>	N lines displayed after the match
grep -B <N> "string" <filename>	N lines displayed before the match
grep -C 2 "Example" <filename>	2 lines from both after and before the match
grep -c "pattern" <filename>	count that how many lines matches
grep -v "pattern" <filename>	display the lines which does not matches
grep -v -e "pattern" -e "pattern" <filename>	does not matches all the given pattern
grep -l "pattern" <filename>*	display only the file names which matches

Other Important Unix commands:

Command	Details
ps -ef| grep cm | awk -F ' ' '{print $2}'	'ps' command to check running process and 'awk' command to select column 2 (delimit values based on space)
sed -n -e '18120, 18130p' <filename>	'sed' command to copy based on line number 18120 to 18130 from a file
sed -i 's/bill/invoice/g' <filename>	'sed' command to replace word bill with invoice in a file
sed -i '/bill/d' <filename>	'sed' command to delete the lines of a file containing "bill" as a string
grep -n "string" <filename> | awk -F ' ' '{print $1}' | cut -d ':' -f1	'cut' command to delimit output by colon and print first field
netstat -a | grep <port-number>	To check if the given port number is in use
top	displays CPU usage, memory usage, running processes
df or du	displays disk space usage
jobs	lists active jobs running
nohup <command> &	executes script/command in background for long running jobs (runs even if current terminal is terminated)
kill, pkill	terminate process using processid (kill) and by process name (pkill)
tail	prints data from the end of a specified file
vi <filename>	widely used text editor in UNIX

Git is widely used as a version control system. Below commands helps in managing files in Git:

git Command	Details
git add <filename>	Add one or more files to be checked-in
git add -u	Adds all tracked files for staging/commiting
grep commit -m "comment"	Commit the files added to be checked in to git branch
git push origin <branchname>	Push or checkin the commit into the branch
git status	Provides information about the Git branch and files status
git branch	Lists the git branches and the current branch checked-out in system
git checkout <branchname>	Checkout/move to a different Git branch
git checkout <branchname> -- <filename>	Get a file from a particular branch in the system
git pull	Fetch all the latest files from current branch
git fetch	Fetch the new branches created from the Git repository
grep reset --hard <branchname>	Forceful checkout to a branch, if git checkout fails due to some reason

Below are some key points to consider for Oracle SQL tuning:

 1. "SELECT" queries tuning tricks. Query performance can be validated using "Explain Plan" option in SQL developer.
     a. Parallel hint (/*+ parallel(8) */) with increased no of threads to perform faster processing.
     b. Using columns with index in where clause of select statements
     c. Using DB partitions to query data
     d. Use WITH clause in select queries, in order to make changes in future easier
     d. Use EXISTS instead of COUNT in queries
     e. Leverage Oracle Json functions (JSON_ARRAYAGG, JSON_VALUE) for multiple columns selection

 2. PL/SQL Performance Improvement - Use BULK COLLECT and FORALL for bulk DML updates for less context switching

 3. Using Oracle SQL Developer tool
    a. Query performance analysis using explain plan
    b. Export data to xls or clipboard
    c. Import data into table using "sqlldr" utility from unix (faster compared to insert queries)
    d. SQL Developer shortcuts:
      Ctrl+F7: Format SQL query
      Shift+F4: Opens a describe window for current object/table at cursor
      F10: SQL cost estimate (Explain Plan)

If any Oracle Database transaction is taking longer time than expected, most likely the DB query processing is stuck or waiting for another session to complete.

Below queries are useful to identify the long running queries: