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Delimited identifiers means identifiers enclosed in double quotation marks. They can contain characters normally not supported in SQL identifiers, and they can be identical to a reserved word, e.g. a column named YEAR is specified as "YEAR". In MySQL, double quotes are string literal delimiters by default instead.
A delimiter is a sequence of one or more characters for specifying the boundary between separate, independent regions in plain text, mathematical expressions or other data streams. [1] [2] An example of a delimiter is the comma character, which acts as a field delimiter in a sequence of comma-separated values.
CSV is a delimited text file that uses a comma to separate values (many implementations of CSV import/export tools allow other separators to be used; for example, the use of a "Sep=^" row as the first row in the *.csv file will cause Excel to open the file expecting caret "^" to be the separator instead of comma ","). Simple CSV implementations ...
A delimited text file is a text file used to store data, in which each line represents a single book, company, or other thing, and each line has fields separated by the delimiter. [3] Compared to the kind of flat file that uses spaces to force every field to the same width, a delimited file has the advantage of allowing field values of any length.
In delimiter-separated values files, the fields are separated by a character or string called the delimiter.Common variants are comma-separated values (CSV) where the delimiter is a comma, tab-separated values (TSV) where the delimiter is the tab character), space-separated values and vertical-bar-separated values (delimiter is |).
The TSV format is thus a delimiter-separated values format, similar to comma-separated values. TSV is a simple file format that is widely supported, so it is often used in data exchange to move tabular data between different computer programs that support the format.
SELECT list is the list of columns or SQL expressions to be returned by the query. This is approximately the relational algebra projection operation. AS optionally provides an alias for each column or expression in the SELECT list. This is the relational algebra rename operation. FROM specifies from which table to get the data. [3]
In SQL (Structured Query Language), the term cardinality refers to the uniqueness of data values contained in a particular column (attribute) of a database table. The lower the cardinality, the more duplicated elements in a column. Thus, a column with the lowest possible cardinality would have the same value for every row.