10/29: Web ＞ スタイルシート ＞ レイヤー
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<div style="position:relative; width:480px; margin-left:auto; margin-right:auto; padding:0px;"> （親）
<div style="position:absolute; top:0px; left:0px; width:480px; z-index:10; text-align:left; margin:0px; padding:0px;">
例：
<div style="position:relative; width:480px; margin-left:auto; margin-right:auto; padding:0px;"> （親）
<div style="position:absolute; top:0px; left:0px; width:480px; z-index:10; text-align:left; margin:0px; padding:0px;">
10/29: MySQL > SQL Expressions
Numeric Expressions
When numbers are used in an arithmetic or comparison operation, the result may depend on whether it involves exact or approximate values. For example:
SELECT 1.1+2.2=3.3 as 'exact', 1.1E0+2.2E0=3.3E0 as 'approx.';
The column 'exact' returns true (1), but 'approx' returns false (0).
String Expressions
Double quotes can't be used if the ANSI_QUOTES SQL mode is enabled.
The || operator can be used for string concatenation if the PIPES_AS_CONCAT SQL mode is enabled.
The default character set and collation for literal strings depend on the values of the character_set_connection (the default is latin1) and collation_connection (the default is latin1_swedish_ci) system variables.
A non-binary string can be treated as a binary string by preceding it with the BINARY keyword. For example:
SELECT BINARY 'Hello' = 'hello'; (returns FALSE(0))
If ether string in a comparison is binary, both strings are treated as binary.
String comparison rules also apply to ORDER BY, GROUP BY and DISTINCT operations.
LENGTH() returns the length of a string in bytes, whereas CHAR_LENGTH() returns the length in characters.
The UPPER() and LOWER() functions perform case conversion only if the argument is a non-binary string. To make the two functions perform case conversion for a binary string, convert it to a non-binary string like below:
SELECT UPPER((CONVERT(BINARY 'AbCd' USING latin1));
MySQL allows use of LIKE with non-string values by converting non-string values to strings before performing the pattern match.
When numbers are used in an arithmetic or comparison operation, the result may depend on whether it involves exact or approximate values. For example:
SELECT 1.1+2.2=3.3 as 'exact', 1.1E0+2.2E0=3.3E0 as 'approx.';
The column 'exact' returns true (1), but 'approx' returns false (0).
String Expressions
Double quotes can't be used if the ANSI_QUOTES SQL mode is enabled.
The || operator can be used for string concatenation if the PIPES_AS_CONCAT SQL mode is enabled.
The default character set and collation for literal strings depend on the values of the character_set_connection (the default is latin1) and collation_connection (the default is latin1_swedish_ci) system variables.
A non-binary string can be treated as a binary string by preceding it with the BINARY keyword. For example:
SELECT BINARY 'Hello' = 'hello'; (returns FALSE(0))
If ether string in a comparison is binary, both strings are treated as binary.
String comparison rules also apply to ORDER BY, GROUP BY and DISTINCT operations.
LENGTH() returns the length of a string in bytes, whereas CHAR_LENGTH() returns the length in characters.
The UPPER() and LOWER() functions perform case conversion only if the argument is a non-binary string. To make the two functions perform case conversion for a binary string, convert it to a non-binary string like below:
SELECT UPPER((CONVERT(BINARY 'AbCd' USING latin1));
MySQL allows use of LIKE with non-string values by converting non-string values to strings before performing the pattern match.
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