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How to find gaps in sequential numbering in mysql?
...orked for me to find the gaps in a table with more than 80k rows:
SELECT
CONCAT(z.expected, IF(z.got-1>z.expected, CONCAT(' thru ',z.got-1), '')) AS missing
FROM (
SELECT
@rownum:=@rownum+1 AS expected,
IF(@rownum=YourCol, 0, @rownum:=YourCol) AS got
FROM
(SELECT @rownum:=0) AS a
JOIN...
Large, persistent DataFrame in pandas
...o read the file in smaller pieces (use iterator=True, chunksize=1000) then concatenate then with pd.concat. The problem comes in when you pull the entire text file into memory in one big slurp.
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How to convert a color integer to a hex String in Android?
...
private static String To00Hex(int value) {
String hex = "00".concat(Integer.toHexString(value));
return hex.substring(hex.length()-2, hex.length());
}
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String vs. StringBuilder
...ance difference is significant. See the KB article "How to improve string concatenation performance in Visual C#".
I have always tried to code for clarity first, and then optimize for performance later. That's much easier than doing it the other way around! However, having seen the enormous perfo...
Concat all strings inside a List using LINQ
Is there any easy LINQ expression to concatenate my entire List<string> collection items to a single string with a delimiter character?
...
Spring JPA @Query with LIKE
...orks for me):
@Query("SELECT u.username FROM User u WHERE u.username LIKE CONCAT('%',:username,'%')")
List<String> findUsersWithPartOfName(@Param("username") String username);
Notice: The table name in JPQL must start with a capital letter.
...
StringBuilder vs String concatenation in toString() in Java
...s it might not make a
difference, but at what point do you
switch from concat to builder?
At the point where you're concatenating in a loop - that's usually when the compiler can't substitute StringBuilder by itself.
s...
String.Join method that ignores empty strings?
...nce you can do it in SQL directly:
PostgreSQL & MySQL:
SELECT
concat_ws(' / '
, NULLIF(searchTerm1, '')
, NULLIF(searchTerm2, '')
, NULLIF(searchTerm3, '')
, NULLIF(searchTerm4, '')
) AS RPT_SearchTerms;
And even with the glorious MS-SQL-Server it'...
How do I quickly rename a MySQL database (change schema name)?
...ginally suggested the former and someone "improved" my answer to use GROUP_CONCAT. Take your pick, but I prefer the original):
SELECT CONCAT('RENAME TABLE $1.', table_name, ' TO $2.', table_name, '; ')
FROM information_schema.TABLES
WHERE table_schema='$1';
or
SELECT GROUP_CONCAT('RENAME TABLE ...
How to split the name string in mysql?
...
DECLARE delim VARCHAR(1);
SET delim = '|';
SET inipos = 1;
SET fullstr = CONCAT(fullstr, delim);
SET maxlen = LENGTH(fullstr);
REPEAT
SET endpos = LOCATE(delim, fullstr, inipos);
SET item = SUBSTR(fullstr, inipos, endpos - inipos);
IF item <> '' AND item IS NOT NULL THEN ...