41 14.1.1. The COALESCE function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 14.1.2. Firebird 1.0: the *NVL functions . . Comparisons such as “x > y” also return boolean results, but they are generally not called predicates, although this is mainly a matter of form. An expression like Greater( x, y ) that does exactly the Chapter 14. Converting to and from NULL 14.1. Substituting NULL with a value 14.1.1. The COALESCE function The COALESCE function in Firebird 1.5 and higher can convert NULL to most anything else. This enables

Browse previously entered commands Ctrl + R Reverse search for previously entered commands Ctrl + Y Pastes the text in buffer man pages man shows the system’s manual pages. This is the command we use before setting the timestamp will show the same time for execution. echo 'export HISTTIMEFORMAT="%d/%m/%y %T "' >> ~/.bashrc source ~/.bashrc ... ... history Sort files by size You can use -S or –sort=size management tool. These are the ways to install it in Fedora and in Debian/Ubuntu $ sudo dnf install htop -y $ sudo apt-get install htop To know more about htop, please read the man page. $ man htop More about

Browse previously entered commands Ctrl + R Reverse search for previously entered commands Ctrl + Y Pastes the text in buffer 1.21 man pages man shows the system’s manual pages. This is the command before setting the timestamp will show the same time for execution. echo 'export HISTTIMEFORMAT="%d/%m/%y %T "' >> ~/.bashrc source ~/.bashrc ... ... history 3.20 Sort files by size You can use -S or –sort=size command 39 Linux command line for you and me Documentation, Release 0.1 $ sudo dnf install htop -y $ sudo apt-get install htop To know more about htop, please read the man page. $ man htop 7.9 More

types Y Y Y Y Y Y Date and time types Y Y Y Y Y Y String types Y Y Y Y Y Y JSON type Experimental Experimental Experimental Experimental Experimental Experimental Control flow functions Y Y Y Y Y Y String String functions Y Y Y Y Y Y Numeric functions and operators Y Y Y Y Y Y Date and time functions Y Y Y Y Y Y Bit functions and operators Y Y Y Y Y Y Cast functions and operators Y Y Y Y Y Y Encryption compression functions Y Y Y Y Y Y Information functions Y Y Y Y Y Y JSON functions Experimental Experimental Experimental Experimental Experimental Experimental Aggregation functions Y Y Y Y Y Y Window functions

....................................................................................215 9.16.2. COALESCE ............................................................................................... ambiguity. For example, if you have defined a left unary operator named @, you cannot write X*@Y; you must write X* @Y to ensure that PostgreSQL reads it as two operator names not one. 4.1.4. Special Characters avoid division by zero in a WHERE clause: SELECT ... WHERE x > 0 AND y/x > 1.5; But this is safe: SELECT ... WHERE CASE WHEN x > 0 THEN y/x > 1.5 ELSE false END; A CASE construct used in this fashion will

....................................................................................203 9.16.2. COALESCE ............................................................................................... ambiguity. For example, if you have defined a left unary operator named @, you cannot write X*@Y; you must write X* @Y to ensure that PostgreSQL reads it as two operator names not one. 4.1.4. Special Characters avoid division by zero in a WHERE clause: SELECT ... WHERE x > 0 AND y/x > 1.5; But this is safe: SELECT ... WHERE CASE WHEN x > 0 THEN y/x > 1.5 ELSE false END; A CASE construct used in this fashion will

....................................................................................188 9.13.2. COALESCE ............................................................................................... ambiguity. For example, if you have defined a left unary operator named @, you cannot write X*@Y; you must write X* @Y to ensure that PostgreSQL reads it as two operator names not one. 4.1.4. Special Characters division by zero in a WHERE clause: SELECT ... WHERE x < > 0 AND y/x > 1.5; But this is safe: SELECT ... WHERE CASE WHEN x < > 0 THEN y/x > 1.5 ELSE false END; A CASE construct used in this fashion will

....................................................................................218 9.16.2. COALESCE ............................................................................................... ambiguity. For example, if you have defined a left unary operator named @, you cannot write X*@Y; you must write X* @Y to ensure that PostgreSQL reads it as two operator names not one. 4.1.4. Special Characters parameter-less aggregate functions as window functions, for example count(*) OVER (PARTITION BY x ORDER BY y). * is customarily not used for non- aggregate window functions. Aggregate window functions, unlike

....................................................................................232 9.16.2. COALESCE ............................................................................................... ambiguity. For example, if you have defined a left unary operator named @, you cannot write X*@Y; you must write X* @Y to ensure that PostgreSQL reads it as two operator names not one. 4.1.4. Special Characters parameter-less aggregate functions as window functions, for example count(*) OVER (PARTITION BY x ORDER BY y). * is customarily not used for non-aggregate window functions. Aggregate window functions, unlike normal

....................................................................................240 9.16.2. COALESCE ............................................................................................... ambiguity. For example, if you have defined a left unary operator named @, you cannot write X*@Y; you must write X* @Y to ensure that PostgreSQL reads it as two operator names not one. 4.1.4. Special Characters parameter-less aggregate functions as window functions, for example count(*) OVER (PARTITION BY x ORDER BY y). * is customarily not used for non-aggregate window functions. Aggregate window functions, unlike normal