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Use \boldsymbol For example: $E = mc^{2}$ After bold italic vectors: \$\boldsymbol{E = mc^{2}}\$, the equation as follows: $\boldsymbol{E = mc^{2}}$

The hear of linear algebra is in two operations -- both with vectors. We add vectors to get $\boldsymbol{v}$ + $\boldsymbol{w}$. We multiply them by numbers $c$ and $d$ to get $c\boldsymbol{v}$ and $d\boldsymbol{w}$. Combining those two operations(adding $c\boldsymbol{v}$ to $d\boldsymbol{w}$) gives the linear combination  $c\boldsymbol{v}$ + $d\boldsymbol{w}$. $c\boldsymbol{v}$ + $d\boldsymbol{w}$ = $c\begin{bmatrix}1\\ 1\end{bmatrix}$ + $d\begin{bmatrix}2\\3\end{bmatrix}$ = $\begin{bmatrix}c + 2d\\c + 3d\end{bmatrix}$ Central ideas of chapter 1: Sections 1.1 Vectors addition $\boldsymbol{v} + \boldsymbol{w}$ and linear combinations $c\boldsymbol{v}$ + $d\boldsymbol{w}$ Sections 1.2 The dot product $\boldsymbol{v} \cdot \boldsymbol{w}$   of two vectors and the length $\lVert \boldsymbol{v} \rVert = \sqrt{\boldsymbol{v} \cdot \boldsymbol{v}}$ Sections 1.3 Matrics $A$, linear equations $Ax = b$, solution $x = A^{-1}b$.

Delete row from table in clickhouse: :) ALTER TABLE tablename DELETE WHERE condition

Change the name of one column: ALTER TABLE tablename RENAME COLUMN old_name TO new_name Change the names of multiple columns: ALTER TABLE tablename     RENAME COLUMN old_name1 TO new_name1,     RENAME COLUMN old_name2 TO new_name2

1. Install py311-pip with root # pkg install py311-pip 2. Install clickhouse_connect by pip with normal user $ pip install clickhouse_connect

Export data from clickhouse into csv file: :) SELECT * FROM table INTO OUTFILE 'file' Import data from csv file: clickhouse-client -q "INSERT INTO database.tablename FORMAT CSV" < tablename.csv

Install command: # pkg install clickhouse Start clickhouse server $ clickhouse server Start clickhouse server without any ouput $ clickhouse server > /dev/null 2>&1 & Start clickhouse client $ clickhouse client

1. Set IP address and default router # ee /etc/rc.conf Add content as following into rc.conf. ifconfig_em0="inet 192.168.1.18 netmask 255.255.255.0" defaultrouter="192.168.1.1" save it, push keyboard buttons ESC ,  A ,  A . 2. Setting up DNS # ee /etc/resolv.conf Content of resolv.conf nameserver 8.8.8.8 nameserver 1.1.1.1 save it, push keyboard buttons  ESC ,  A ,  A . 3. Restart network # sh /etc/rc # /etc/netstart

After I deleted slim package with command "pkg delete". And I installed slim back. But when I login to my FreeBSD and the error message comes out as following: I am sure I enter the right username and password. And I use the root to login, I got the same result. Solution: Press Keyboard "Ctrl" , "Alt" and "F1" or "F2"  and it will go to the terminal as following: I can login now.