Quotes around INSERT and SELECT statements' arguments from the mysql CLI and PHP

[Dotan Cohen]

I am somewhat confused as to the proper way to place quotes around
arguments in INSERT and SELECT statements. I also don't see where this
is made explicit in the fine manual.

If the column is type int, is it preferable to use single, double, or
no quotes on INSERT from the mysql cli?
If the column is type int, is it preferable to use single, double, or
no quotes on SELECT from the mysql cli?
If the column is type int, is it preferable to use single, double, or
no quotes on INSERT from PHP?
If the column is type int, is it preferable to use single, double, or
no quotes on SELECT from PHP?
Is it the same for decimal and float?

If the column is type varchar, is it preferable to use single or
double quotes on INSERT from the mysql cli?
If the column is type varchar, is it preferable to use single or
double quotes on SELECT from the mysql cli?
If the column is type varchar, is it preferable to use single or
double quotes on INSERT from PHP?
If the column is type varchar, is it preferable to use single or
double quotes on SELECT from PHP?
Is it the same for text and blob?
Also, in PHP often I see code examples with the variable wrapped in
curly brackets, inside single quotes. What is the purpose of the curly
brackets? Here is such an example:
$query="INSERT INTO names (name) VALUE ('{$userName}')";

If the column is type datetime, is it preferable to use single or
double quotes on INSERT from the mysql cli?
If the column is type datetime, is it preferable to use single or
double quotes on SELECT from the mysql cli?
If the column is type datetime, is it preferable to use single or
double quotes on INSERT from PHP?
If the column is type datetime, is it preferable to use single or
double quotes on SELECT from PHP?
What if I am using the NOW() function?

If the column is type set, is it preferable to use single or double
quotes on INSERT from the mysql cli?
If the column is type set, is it preferable to use single or double
quotes on SELECT from the mysql cli?
If the column is type set, is it preferable to use single or double
quotes on INSERT from PHP?
If the column is type set, is it preferable to use single or double
quotes on SELECT from PHP?

Thanks.

-- 
Dotan Cohen

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