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How do I add indices to MySQL tables?
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In MySQL, if you use ALTER TABLE tbl ADD INDEX (col) instead of ALTER TABLE tbl ADD INDEX col (col), then using ALTER TABLE tbl ADD INDEX (col) more than once will keep adding indices named col_2,col_3,... each time. Whereas using ALTER TABLE tbl ADD INDEX c...
MySQL InnoDB not releasing disk space after deleting data rows from table
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Yes, just "OPTIMIZE TABLE tbl_name;" and mysql restart
– Vit
Sep 17 at 8:10
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Splitting string into multiple rows in Oracle
...reate a collection type to hold the results
CREATE OR REPLACE TYPE typ_str2tbl_nst AS TABLE OF VARCHAR2(30);
/
-- Split the string according to the specified delimiter
CREATE OR REPLACE FUNCTION str2tbl (
p_string VARCHAR2,
p_delimiter CHAR DEFAULT ','
)
RETURN typ_str2tbl_nst PIPELINED
AS
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从一个开发的角度看负载均衡和LVS - 更多技术 - 清泛网 - 专注C/C++及内核技术
...，返回的时候不经过LVS。
DR模式下需要LVS和绑定同一个VIP（RS通过将VIP绑定在loopback实现）。
一个请求过来时，LVS只需要将网络帧的MAC地址修改为某一台RS的MAC，该包就会被转发到相应的RS处理，注意此时的源IP和目标IP都没...
PostgreSQL LIKE query performance variations
...ILIKE patterns, not just left-anchored ones:
Example index:
CREATE INDEX tbl_col_gin_trgm_idx ON tbl USING gin (col gin_trgm_ops);
Or:
CREATE INDEX tbl_col_gist_trgm_idx ON tbl USING gist (col gist_trgm_ops);
Difference between GiST and GIN index
Example query:
SELECT * FROM tbl WHERE col...
Programmatically creating Markdown tables in R with KnitR
... Var2=sample(x=c("Dog","Cat","Bunny"),size=40,replace=TRUE))
tbl1 <- table(my.df$Var1,my.df$Var2)
tbl1 <- cbind(tbl1,rowSums(tbl1))
tbl1 <- rbind(tbl1,colSums(tbl1))
colnames(tbl1)[4] <- "TOTAL"
rownames(tbl1)[4] <- "TOTAL"
# Because I used results='asis' for this chu...
Comparing Dates in Oracle SQL
...to get it to display the number of employees that are hired after June 20, 1994,
But I get an error saying "JUN' invalid identifier. Please help, thanks!
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Extract a dplyr tbl column as a vector
Is there a more succinct way to get one column of a dplyr tbl as a vector, from a tbl with database back-end (i.e. the data frame/table can't be subset directly)?
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SQL Inner-join with 3 tables?
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SELECT column_Name1,column_name2,......
From tbl_name1,tbl_name2,tbl_name3
where tbl_name1.column_name = tbl_name2.column_name
and tbl_name2.column_name = tbl_name3.column_name
share
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Dropping Unique constraint from MySQL table
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A unique constraint is also an index.
First use SHOW INDEX FROM tbl_name to find out the name of the index. The name of the index is stored in the column called key_name in the results of that query.
Then you can use DROP INDEX:
DROP INDEX index_name ON tbl_name
or the ALTER TABLE syn...