Turn on or off color syntax highlighting in vi or vim editor

Vim or vi is a text editor. It can be used to edit all kinds of plain text. It is especially useful for editing programs or UNIX/Linux configuration files.Turn on syntax highlighting: Open file (for example test.sh):$ vi test.shNow press ESC key to enter into command mode then type  ” : syntax on OR syn on”:syntax onOR:syn onThat’s it.. the color syntax highlighting will be enabled until you close that file (useful when you working on server where you can’t enable it permanently because of restriction and not...

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mysql optimizer Index strategy

If the table has a multiple-column index, any leftmost prefix of the index can be used by the optimizer to find rows. For example, if you have a three-column index on (col1, col2, col3), you have indexed search capabilities on (col1), (col1, col2), and (col1, col2, col3). MySQL cannot use an index if the columns do not form a leftmost prefix of the index. Suppose that you have the SELECT statements shown here: SELECT * FROM tbl_name WHERE col1=val1;SELECT * FROM tbl_name WHERE col1=val1 AND col2=val2; SELECT * FROM...

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